I don't have an anterior placenta but at around 25 weeks I was able to feel movements through out the day but not consistently
I would get movements first thing, around lunch, around 5pm, at dinner time and when I was going to sleep. It varied from day to day but I would usually feel her in 2 - 3 of those time slots each day. So Monday I might feel her first thing, at 5 then when going to sleep but Tuesday it would be lunchtime, evening and going to sleep, Wednesday first thing lunchtime evening. I still had to concentrate on her movements to feel them so if I had a busy day I might not feel her at all until I stopped work in the evenings. On these days I made a point of lying with a glass of water and counting the kicks on an app. There were also days where she was just quiet so I did the same then.
After about 28 weeks her movements got more forceful so it didn't take as much effort to monitor her movements she stuck to the original pattern for a while just with me being able to feel in most of the slots in most days. Some days there would still be times I wouldn't feel her.
At 31 weeks I had a day of reduced movements and since then I think her pattern has changed and I feel her most of the day and less in the early evening then most of the night or if I am lay down. Now the movements are more like pushed outwards as if she is continually stretching.
The day I had reduced movements something felt wrong all day, I called triage in the afternoon and they were lovely. I went in for monitoring and all was OK, she stayed quiet for a few hours after I got home but was then active again. Don't be afraid to call and always do it the day you are worried don't wait until the next day.