From time to time people run into this issue: https://processwire.com/talk/topic/13089-repeater-field-limits-and-server-timeouts/ So the idea is simple: Admin > Setup > Fields > Details (tab) > Maximum items allowed / 0 = No limit Something like the one for images.
And may be a nice little yellow boxed notice underneath, about why it is a good idea to impose a limit...
I love these inline help bits, they help me a lot.
EDIT: I forgot to add that - of course - we also need some GUI voodoo to support it.