It is risky but you can certain small amount kept on exchanges.
Why is that good? You can react fast if dump occurs or wait for alts to wake up like Dogecoin recently
To think on holding or storing bitcoins in a multiple ways is a good idea to lessen the risk on each way of holding. In exchange you can also to do simple trading like selling when its and buying when its low and also you are right you can monitor the price of bitcoin using the scale and you can easily predict on how you are going to manage your bitcoin. Me personally I store my bitcoin on different wallets where I can spend and save at the same time. Because on choosing a wallet you can see that there are more variance on choosing an appropriate wallet the will suits to you.