Personal Force reservoir

The Personal Force reservoir refers to the amount of using of the Force that a Force user individual can perform before fatigue.

Several Force powers have different demands of concentration and endurance than others. Continuous usage of the powers would result in "Force fatigue" but the user's condition could be restored with rest and meditation.

Corran Horn's referred to his "personal Force resevoir", during his training at the Jedi Praxeum.

The excessive use of the battle meditation Force technique by Darth Caedus during the Battle of Fondor rendered him "thin-stretched" and unable to move or think clearly for a while, clearly demonstrating the limitations of force usage. It is fairly likely that these limitations referred much to mental limitations and also the inability of the body to withstand continual use of external energies.

Count Dooku experienced some waning and waxing of his strength with the Force during the duel on the Invisible Hand. In this case, Dooku's over-reliance on the Dark Side leads to "Force exhaustion" temporarily shutting down his natural Force senses. In several instances this fatigue is suggested to be heavily linked to Dooku's state of mind, with his strength being restored by a moment's introspection.

Behind the scenes
The concept of Force repository appears mainly in Lucasarts games and is probably a game mechanic. By using Force powers, the pool wears out, and replenishes slowly with time/rest. Its role in games is to simulate the natural limitations (such as fatigue, concentration, experience) of a user, while its gameplay value is the same as the 'mana pool' of fantasy games; such measures prohibit the player using all of his powers every moment and therefore urges him/her to strategically choose the best time for each action rather than using them recklessly.

In the wider EU nothing hints that the Jedi have a finite (replenishable) repository of powers; it's notable however that in the movies and all other works, the Jedi characters are never seen continuously using their powers during fighting, something they certainly would do, if they could.

This suggests that the Jedi had some limitations to the usage of powers.

However the exact mechanism of these limitations is unknown and almost certainly not so mathematically precise as the 'Force mana' of the video games.