This is common, and will continue to happen. The reason is that half reviews seems to be done by bots and the other half by your peers. Bots do things faster. I'm unsure if this is true or not, however given the mounting proof of my peers, I am starting to believe it.
Currently there are no other ways to speed things up. PR is the fastest way, depending on how many other people are boosting their product through doing PR this can go super fast, or super slow still. It also depends on how many things you PR to boost your things through. Like don't think that you can just do 5 things and they will zoom through lol. 50 might make that happen, but again it will depend on how many people are doing the same thing you are.
Hope this helps