There is no limit on the number of times you can apply to MBB firms over your lifetime. However, most offices have a time restriction in terms of time after being rejected before you can apply again - usually 1-1.5 years.
There are several exceptions to this rule. If you first apply for an internship, you are generally allowed to reapply for full time less than a year later. If you were on the border and didn't make it in your final round, firms will sometimes invite you to reapply in 6-12 months, or if you network with people at the firm they will be able to convince recruiting to make an exception and give you another chance.