Timed blowjobs. is it normal?

In my last relationship I loved the idea of my GF sucking me off for a pre-determined time period (especially because she was quite good at it).

We didn't actually do it, but I wanted to.

I had the fantasy of her going down on me while I set a stopwatch or alarm clock for say, 15 or 30 mins. (I would also have been happy to do the same for her.)

However she was kind of prudish (e.g. she never engaged in doggy style sex, or mirrors, porn, or sex toys) and I believe she would not have done it even if I asked.

I found the idea of timed blow jobs a real turn on.

Is it normal?