I just spread my bitcoins over multiple wallets (lesser than 4

since I'm poor : but i do make sure that theyre all secured). Though I do also hold some bitcoins over a trading site. I might go paper if I can actually make bank but I doubt that's happening anytime soon lol
Be careful with holding your money on trading websites. I'm doing that too but I only have a sum of $0.3 on the trading site. I recommend you to withdraw a part of it if there is a considerable sum deposited.
Yeah its good not to put all your money in trading sites as it can be risky as that trading site can disappear in future but I am using Poloniex since long time and I think that is the trusted place to keep your money but the best choice is to save your bitcoins in offline wallet.