Question: There's a certain kind of people who like to hoard whatever limited resources they get "just in case"; they usually end up never using them, always waiting for bigger emergency. On the other hand, there are game mechanics based on spending some limited resourse: like bennies in Savage Worlds, fortune points in Warhammer, etc. You're supposed to spend them liberally, getting some in-game benefits. 

The "hoarders" never spend these, robbing themselves of part of enjoyment. Simply explaining that "those point are meant to be spent" doesn't always work: players seem to understand that rationally, but some force of habit still prevents them from actually using their resources. I think this happens more often in videogames (I myself am guilty of hoarding all goodies till the end boss, and then never needing them), but I've seen this kind of behaviour in tabletop games too. 

Of course, some players do this because they just like hoarding, or because they like the additional challenge, but some do notice that they're "doing it wrong."

Is there maybe some sort of trick to encourage resource spending? 

**Clarification**
I'm mostly interested in "mechanical" resources like fate points and bennies. If you hoard something material, like potions, or money, at least you (probably) have more money as a result. When you hoard bennies, you essentially forfeit your chance to *do* something that matters. This is probably not what players want.

Answer: 
Interesting question and one that I'm gonna have to solve soon too for my gaming group has similar issues (They don't hoard. They sell it all to buy permanent magic items. But as you can see at least half of the solution I've adopted will apply to both situations.)

This mission/session only
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The first half of the solution is taken from a videogame called Thief.  

At the end of each mission you lose all your unused items and keep every treasure you collected during that mission.  

At the beginning of the next mission, you can use that treasure to buy a wide array of arrows and other trinkets.

You might apply a similar strategy to your missions or even sessions, that heavily depends on your tastes and needs.

This applies greatly to mechanical resources as you requested in your clarification! But often potions and the like are just supposed to be used and not converted to some other type of advantage.  

Let's take it to the next step:

The percentile issue
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The second half of the solution takes care of what happens if, seeing that these items are gonna disappear soon, the players try to monetize them.  

Choose a percentage of treasure that should only be used to buy (or should be made of) consumables, while maybe the other treasure can't be used to buy potions and the like. (In this case remember to always include tham in your treasure parcels.)  

In my D&D 3.5 game that would be 10% as suggested by the books.
Even if they sell those goods, that gold can only be used to buy different consumables (maybe a parallel economy system with different coins?).
Another possibility besides "limited inventory/carry weight" and "expiry date" is **inflation**. Have the resources become worth less, the more the game advances.

At the start of the game, 10 gold is a lot of money. Mid-campaign, every common thief carries 50 gold, shopkeepers have raised their prices. You were better off spending the gold than hoarding it, since it's worth nothing.