So, yes, there is a risk your transaction will take a while if the network is busy and you have to time it right to get a free slot on the accelerator, but I've never waited more than a couple of hours...
If you don't want to wait and/or are somewhat "risk averse" pay the recommended fees and stop trying to cheap out on fees...
Cheap fees+accelerator+high risk or recommended fees+low risk... Pick one combination for fast confirmation times.
I know which one I use