When trying naturally I was told to start after ovulation and if bfn at end of cycle wean off and the start again after next ovulation. It's not good for fertility to be on it for an extended period while ttc. The pp in the nk cells thread was put on it for an extended period while ttc and she stopped ovulating but not sure if it correlates. I was on 10mg after ovulation and then told to double it on bfp. If bfn, wean down to 5mg for a couple of days then 2.5 for a couple of days then nothing. The issue with ttc is that you don't know when it will happen so you could end up on it for a really long time, not great for your body.
Re side effects, I had insomnia as I was told to take it morning and night at first but then changes to morning and lunch and I was fine even on the higher dose. I did gain weight once I was on the higher dose as I was starving and I did get fluffy hair on my face and chin. Once I was 16 weeks I started weaning and when I was down to 10mg it all started to go away and was completely gone a few weeks later. It can deplete your calcium so it's really important to take Caltrate plus each day. Good luck!