I actively use about two or three addresses at any given time, one of which was the first address I ever used. These addresses comprise my "hot" wallet. In total, I have probably used about 10 addresses including change addresses. About half of all the addresses I used were generated via Electrum's deterministic seed feature. The rest are/were addresses generated using Vanitygen which comprise(d) my "cold" wallet.
It is a good habit to never use a receiving address more than once.
Depends, if all you do is keep bitcoins in them no. As soon as you use them (i.e. spend the coins etc..) you should not use that key again, the process of spending actually removes one of the two layers of the security (RIPEMD).
These statements seem to contradict each other. So security-wise, there is nothing wrong with depositing multiple times into a cold paper wallet address right? Just as long as the bitcoins in that cold wallet are never spent?
But wouldn't such a cold address also fit the definition of a receiving address as well?