How to increase the durability of gear-shifters I am not a professional cyclist and may not even be a good rider but it seems like I tend to break my shifters way too often.
I initially had a SRAM-X4 8x3 Shifters which ripped apart in an accident. This seems reasonable because the accident was the reason the shifter broke.
So, I upgraded to a Shimano ST-EF50 8x3. This is where the problems seem to arise. Once again, I want to humbly point out that I might not be a good rider and might have put some excessive stress on those shifters than they are meant to withstand but from what I've noticed, after just 8 months of regular 2 hours/day commutes, the 8-speed shifter's top plastic part just popped out. I was speculating that maybe I might have dropped it somewhere quite hard and this might have done some damage to it but for what I was concerned due to my tight schedule it was at least working so I took some masking tape and rolled around the shifter to temporarily hold the plastic so that I can go home and fix it. Since I am a student and I couldn't find any time to fix it and unfortunately so I was forced to ride my cycle without permanently fixing the shifter. After a month, the 8-speed shifter completely failed, all the parts inside started to come out. I understood that it could be my fault to use it without fixing so I didn't think it was the shifter fault.
This model was the standard shifters found in most entry-level cycles so I assumed it would be reliable so I bought another set of the same shifters and to my surprise, the same issue came again after 10 months but this time in both shifters. This time I just bypassed the shifter and kept my 8-speed derailleur in 4th and was riding it doing 2-3 hour/day commutes. I skied off the main road after a car bumped into me. The impact was high and my rear derailleur (Shimano Altus RD-M310) broke completely. I basically left my cycle on dirt for 6 months and thought of doing a complete 8 to 9-speed upgrade.
I bought a brand new Shimano Alivio RD-M4000 and SL-M4000-R and L shifters. I kept the old stock front derailer Shimano Altus FD-M310. Everything was going smooth, I really enjoyed riding my cycle. It felt brand new. I enjoyed it so much that I took it for 8 hour/8-10 km drives 3 days once and that was the end of the happiness. 1 year later, it happened again. The shifters broke but this time only the left 3-speed one. Right now I am convinced that there's something in my driving style causing the damage. I don't know what is causing the damage but what I do know is there is something which is causing the damage. After some conversations with my biking community, it seems like it is common for gear shifters to fail and I want to know if this is true. My objective is to use your amazing expertise to advise noob cyclist such as myself on how to use the gear shifters and to find the answers to the following questions.

Will the way we're using the shifters affects its durability?
If so then how to prevent it?
Are there more durable shifters in the market then mentioned above?
Are there any other miscellaneous advice regarding gear shifter you'd like to provide for the new and upcoming cycling enthusiasts?

Thank you so much for your valuable time.
PS: I'd like to point out that all the parts mentioned above were bought in an authorized showroom. The cycle was bought from Decathlon and is a Rockrider 5.2.
Initially, it was shipped with a SRAM X-4 8-speed and now after many upgrades, it has a Shimano Alivio RD-M4000 9-speed as mentioned previously. I do know it's expensive to upgrade each part rather than buy a new cycle with the better parts. The sole reason I am sticking to this cycle is for sentimental purposes.
There are a few ways that user habits or mechanical adjustment can negatively effect durability:

If you downshift the right or upshift the left when the cranks aren't moving, you'll be putting excess force through the internal parts. A little bit of this isn't a big deal, but doing it habitually can break shifters.
Left shifters sometimes fail prematurely due to a combination of too much cable tension and the front derailleur high limit screw being set in enough that it causes the shifter to be held under tension when in the large chainring position. What happens then is that when shifting into the middle ring position, the release lever push is very hard and excess force is put through the shifter.
Some people shift more than others. This has an impact on shifter lifespan.
Shifters need their internal lubrication, and some environments are harder on it than others. Usually this would not explain the kinds of failure you're talking about, but sufficiently rainy/salty environments could prove an exception, especially if the bike is stored outside. Shimano trigger shifters are factory lubricated with a few strategically placed globs of highly washout resistant grease, which can be carefully replenished if things do get dry inside.
Some cyclists ram the shift levers with arbitrary amounts of force and others have shifting technique that's more calibrated to the fact that there are internal parts sliding past each other inside making it all work. The former will wear out shifters faster. Usually the difference will be fairly minor, but again it's conceivable for more extreme cases to prove an exception.

Shifters get more durable the further up in the product line hierarchies they are. Someone riding as much as you describe is generally speaking going to be the kind of cyclist that benefits from getting mid-range or better components, i.e. Deore. That said, all trigger style shifters could suffer and break from the above conditions, and I'd suspect there's some cause other than putting a lot of use through low-end shifters that's causing the failures.
The highest durability compatible indexing shifters you could get are Shimano SL-BS77 bar-ends mounted to something like Paul Thumbie mounts. The ball detent based indexing they use handles force in a very different manner than pawl type indexing, and they are more inured to some of the above problems. That doesn't mean that going that direction necessarily makes sense given the expense, or is the only solution.