I will start off with the quick answer...there is no way to limit the extensions to say 10 extensions.
Now, having said that, there are ways to encourage more or less extensions by the extension rules, for example, increasing the increment size or only trigger extensions for bids that beat the lead bid.
But, I have to ask, why would you want to limit the extensions? If you have the event setup properly, each extension is most likely saving you more money, right? Are you saying the incremental savings for each extension is not worth enough to sit through another extension? If so, then adjust the settings to make the "cost" of triggering an extension more significant.