Can you have too many in line barrel adjusters? Just replacing the shifters on my bike. It had STI shifters and I'm putting thumb shifters on, the shifters have built in barrel adjusters.

The bike also came with barrel adjusters on the down tube, and there is an adjuster on the rear mech. This means that the cable for the rear mech will have three adjusters along its course.

Is there any reason to not have too many adjusters?

I could take the down tube adjusters off without it looking bad (they're not on bosses), but would like to keep them if there's no downside as they are a bit easier to operate that the ones built into the brakes.

Thanks
I don't think so, as long as you have correct cable housing and ferrules where you need them, there's no problem having multiple barrel adjusters. If you know how to use them then there's no downside to having three in my opinion. 

Try it and let us know!