I have reused my coco/perlite a few times, with mixed results. I think the root hairs left from previous grows compost in there. Eventually the coco might become more like soil and less like coco. Recycled coco with gnat eggs might have hurt my seedling survival rate last time. Next run I'm going to use new coco, it's so cheap, like $3 per 3-gallon pot. I'm using the cheapest 5-kilo coco brick, good for maybe 8 or 10 3-gallon pots. I rinse it in a sieve over the laundry sink, and soak for 8 hours in 7 ml per gallon of CalMag to buffer it before I add the perlite. Last time I used this brand, but i didn't see any difference from Mother Earth or another brand I got off eBay or HomeDespot:
Coconut coir bricks are composed of three different types of compressed coconut coir. The brick will break down on its own in three years. 100% organic coir fiber. 100% natural coir material that has been flushed of excess sodium.
www.ebay.com