I have got around 1000 Novacoins in stacks of 20-100 Novacoins and stake a block once every few days.
Really? My blocks are bigger and they take a long time to stake! What wallet version are you using?
Same number of coins stakes less often if they are in few big blocks than if they are in many small blocks. The total profit from staking is about the same. With smaller blocks it is just earned in more smaller stakes.
This is a bit complicated to explain. The reason for this behaviour is the 30 day maturation period in which blocks do not stake at all. With bigger blocks, your coins spend more time within that maturation period. With smaller blocks, each individual block stakes later because of the smaller coin day weight. Staking later means spending less time within the 30 day maturation period. So despite each individual block staking later, in total you stake more more often.
I usually get 1-4 Novacoin per block that I stake. Your average reward is probably higher.
You should also avoid having blocks larger than 150 NVC, because they have a greater risk of hitting the max reward cap of 10 NVC.
I can't check my client version right now, I think I am using Novacoin 0.5.6., but it should not matter.