I don't think there is a hard limit but Browser performance will decrease with very wide repeating sections or a very high amount of controls.
what are you going to achieve?
I'm as well not aware of any limits, but experienced problems to design a form with very wide repeating section - controls that I placed or wanted to place far too right were regularly jumping to the middle of repeater row.
as well I got negative feedback from users when they still had to use scrollbars to move to the right.
and if I recall correctly in some browsers such forms rendered with two horizontal scrollbars, one for page a second one for repeating section. so not very handy to use.