stylus condition and maintenance

Just use them!

They can last a very long time, however you must learn how to setup the turntable, arm/cartridge and stylus cleaning, which can be tricky!

Just judge the quality, by the sound of your system, and relax!

You may be on a LONG enjoyable trip.

another route is to get/borrow a 100x or greater microscope and look at the cantilever and stylus. That should tell you if they are straight and/or worn on one side or the other.
Listening though is the final test.

The suspension goes out before the tip many times so change cartgs. every 3-4 years to keep them in good shape. Using a 10 yr. old cartridge is not a good idea. The suspension just gets tired and wears out, and the compliance is not as new. I change every 3-4 years. Use tweak heavily on the styli and you will need to change every year. A small amt. is all that is needed, otherwise it will wick up into the cart.