When do naps become reliable?

[WantToMoveNorth]

My DTs are almost 5.5 months old and I'm really trying to get their daytime naps sorted. I'm trying to stick to a routine, but I find some days one twin only naps for 45 mins (and they end up very overtired) and the other DT has a nap for over 2 hrs! Most days they both have short naps- i dont often get them both having long naps! Do you know when naps become more reliable? I.e they have a long lunchtime nap? I know they are doing pretty well for 5 months, I just find it hard dealing with 2 overtired babies so would like an idea when it is likely to end! I'm also desperate to get them in a routine, just to give me a bit more time with my older DD.

Thanks!

I think around 8/9 months I knew when she would have a sleep and how long for. Literally within 5 minutes of 11.30 she would nod off for two hours and again at 3.30... She's always been a really good sleeper though, so don't know how common that is.

Hmmm well my dts are nearly a year now and around the 8 month mark they started having a 1.5 hr nap in the morning at the same time then another in the pm, not always t same time. It was great! However that has stopped now!!! Dtg reliably has a morning and afternoon np, dtb is a nightmare, sometimes has one long one sometimes two short. I am crap at routines though! When there were in the napping together period I think it was just a happy coincidence!