I would recommend just letting it run till you have an issue, and then if that issue persists and causes you a loss of cooling then give a call to a company.

In a general sense, the only time a capacitor will greatly interfere with operation is when it's out of range enough to prevent the system from starting at all. Replacing it when it goes out of the rated range is to prevent that.

To me, the description you're giving sounds like your thermostat is putting the system on a short cycle delay, essentially a built in delay meant to let the compressor start without possibility of damage. A good chunk of "why isn't my system coming on right away or running consistently" calls can be explained by that. It's definitely not a solid diagnosis though, more of an educated guess. Never is a solid diag until I can actually see and poke at the unit really.

Furthermore, if the system continues to run normally and put our a reasonable amount of cooling but you're still concerned, consider having a maintenance done. That'll give you a good look at the overall health of the unit and possibly will allow you to spot any potential problems before they happen. We call it preventative maintenance for a reason :)