Should I divide them among multiple addresses and how many?
Separate question - is this a standard practice?
It's not just about dividing into different addresses. If you store an address safely then there is absolutely no need for further cold storage addresses. Sure it makes it safer, but by a tiny margin. If you are storing less than 1 btc there is really no reason to do it.
Try to keep your coins in different wallets altogether.
What I like to do is keep a few bit cents on blockchain.info for day to day btc transactions, keep around 20% of my coins in a desktop wallet and the rest in a trezor wallet.