I do all mine on AAA login through AHIR the day there born its put in, BW and sire. Then it's there ready to go when WW and YW are ready to be added. At weaning is when I decide if I'm gonna register them, even if you don't register them, turn all the data in.
It takes about 30 seconds to put it in, so if I loose my little book, the info is still there. To put it in the calving book costs nothing, when you add WW its 3 dollars, then nothing for YW, all of it needs to be turned in to keep true numbers on your cows.
I don't worry about contemporary groups, unless there born and raised on different farms, you can manipulate numbers in contemporaries, but mine are what they are, turned in at once.