I was restitched when dc1 was 8m. In my case the problem was that part of the internal wound never healed. I was in almost constant discomfort (rather than pain), wiping after the toilet hurt and sex was impossible.
The surgery was straightforward, GA, home within a few hours. Recovery was more painful than I had expected. It hadn't occurred to me that stretching to deliver a baby would have reduced sensation in that area, so I would feel a heck of a lot more this time around. But I recovered very quickly.
The restitching certainly resolved the issue of having a non-healing wound in my vagina, but TBH it did not resolve everything. I still had pain almost whenever I was touched down there. Just nowhere near as bad as before.
Sex life resumed, dc2 was conceived and born very straightforwardly. I tore again on the scar, but not as badly. This time the midwife stitched me (with dc1 it was the registrar) and I healed perfectly. No more pain.
I didn't tear at all with subsequent dc.
Overall I have less sensation now, which is a frustration for sex. I don't know whether that's because of tearing or repairing. I do not regret the repair, and I'm glad we didn't wait longer or try to power through to conceive our dc.