Souring Question

Hi, folks.
I have a question about souring.
I have a 5-gal batch of beer (RR COnsecration clone) and 1-gal of cider in with bug blend.
The RR I brewed end of last summer, racked after primary slowed down and pitched a vial of White Labs bug blend. I didn’t get any hint anything was happenning, so when I did the cider, I used the Wyyeast smack pack, half into the cider and half into the beer.
The cider went well, with a nice pellicle forming within a few weeks, but the beer took longer. Finally around beginning of March it started and by mid month it was a nice coating across the surface.

My main questions are: 1) is it unusual for it to take that long to form on the beer, and
2) how will I know when it’s ready? I keep reading about how you don’t want to disturb the pellicle once formed, but do I break through for a sample now and again, or will it do something to say it’s done?