Fracture is not part of your rotation so you don't keep reapplying it. For me if Demolish have 4-5s before falling off, it's too early to reapply Demolish, so I will apply fracture first. It's done in a way that it doesn't interfere with your normal rotation, doesn't cause your buff/debuff to fall off, otherwise it's going to be a dps loss.

The thing to remember is not to overuse it and causing tp drain on yourself and cause rotational error. TBH I am still not used to using fracture so sometimes I forgot about it, I have mostly use it in A1S, where I don't really need to worry about TP due to the downtime.