I strongly dislike time limits, however sometimes you just can't omit them without the game turning into oblivion.
To make them least aggravating, several guidelines should be followed:
1. Avoid prolonged time limits encompassing entire quest lines and such if possible. They are not fun, not much help and have great fuck-up potential.
2. Apart from things like running away from an especially deadly hazard, limits that result in game-over don't add to the gameplay - add some interesting consequences, be creative and don't allow player to meet all the deadlines, etc.
3. The less unique the quest is, the more stringent time limit is desirable - generated misc quests should have fucking harsh ones, as the consequences of failure can be bad, but unspecific, while unique quests would do best using other devices - including mutual and consequence based exclusivity.
4. Time to receive quest can be all good and dandy if it's balanced out by something (win some, lose some, as Madras would say
).
5. Introducing other kinds of time dependent mechanics, like dwindling supplies makes for a good alternative if you want some unspecific, time based limitations.
RPGs are not arcades, they are not played with beating the game in mind, they should be made possibly interesting and as long as available plot devices, including time limits, are used with this in mind, they can be used to improve them.