i have made it thru my first winter.....now my concern is swarming. when do i need to start worring about swarm cells popping up?

we had some warmer weather a week or so ago and i was able to open the hive for the first time in which i did find eggs. the hives looked really good as far as number of bees. actually more bees than i was expecting to see.

my intent is to split the hives when the weather permits. but i wanted to get that done before any swarming was too much of an issue.

any advise please!!!!