Retiring equiptment...

I go by the rule that if there is a hole, it is not going to be used. One option you can do to salvage the still usable fabric, is to trim away the part of the silk that has the hole and then rig it up with another shorter piece of fabric on the same figure-8. I know of some aerialist who sew up holes, but I am not entirely confident in that option, especially since you are performing so regularly and I assume that you are doing drops in the act.

To answer the second part of your question, I would regularly inspect your silks (once a month is probably a good bet) by completely unrigging it, paying special attention to the area that is rigged as that tends to get the most friction and wear. As for hardware, I think that depends on how ofter you are having to re-rig. If it's a traveling show and there is constant re-rigging of the equipment, you will need to replace it more often since the likelihood of dropping the equipment or just banging around of packing it up can wear it down. If you do maintain a monthly inspection of your things, that is also a good time to clean out the hardware to clear away debris such a dirt, sand, or even small bugs that can find their way in there and cause grating which then lessens the lifespan of it. If you know of a good rigger, it's also a good idea to have them inspect your equipment from time to time as they have better eyes for small details that we as performers might miss. I also believe life span on the hardware varies between aluminum and steal, which I personally do not know. One last thing, I know this is rather long winded, is to not use a mixture of aluminum and steel hardware together (such as an aluminum figure 8 with a steel carabiner). Since steel is a more dense metal than aluminum (or it might be the other way around...I'm not a certified rigger!), the more dense metal will tear into the softer metal, thus weakening it over time. Simply put, stick to one type of metal!

Hope that helps! What show are you in?