Double sleeves on all my non-trade stuff and on all trade stuff above 5$.
Usually I keep binders for the two formats I play with everything sleeved the same way - easy deckbuilding and cards are always protected. As I mainly play oldschool nowaways, it is obvious I want the best protection for my cards, many of them are pretty old and rare.
Spending a hundred dollars to conveniently sleeve everything you play is absolutely worth it - you'd spend the same on a pair of shoes for running or whatever sports equipment. Sometimes we Magic players are obsessed with the thought that we don't actually "spend" money on Magic, but sometimes you should just do it ;-)