I've actually reused my soil on 2 of my 4 plants and I've only just started it but if I started seeing bugs and gnats I think I'd lash it away well as long as it doesn't fly around there welcome to work and do there magic underground
also from having to dump 6 15 litre pots of coco after every grow it's a well deserved change. Anyhow bro if you remember tag me occasionally in your thread as I lose track who I've looked at grower wise as happy to tag along