In general (I do not own DSE601. I have used DSE901 attys)
If it uses an atomizer - you need to have 1 or better 2 spare atomizers. When one gets gunked up and performing badly, you switch to a clean atomizer after priming it with some 3-4
juice drops and waiting for that to soak down to its coil. And you clean the dirty atomizer (I blow it out, then use near boiling water to clean it and soak it, then shake that out, then soak overnight in edible pure grain alcohol, then shake that out, then set it to dry)
If you use cartomizers, get new cartomizers. And I think thin light clear juices make my cartos work better longer (I use 20% or less VG and juices that leave little or no flavoring sediment)
One problem I had with DSE901 attys was they can twist relative to their
threaded end and when that happens their side air intake can become partially blocked by some kind of plastic armature that is in the coil compartment. That is hard to fix.