You have to decide this as well (or choose not to make a limitation). But this limitation helped drive a lot of future decisions. For instance when we closed a massive deal and that client became more than 12%, we’d celebrate, but then quickly get back to finding another big deal / growing a client to offset this new big client. We really never let ourselves get excited about the big deal, we got excited when they were diluted below 12%.
Keep in mind people wil judge you by your weakest offering, not your strongest, even if your weakest is only 2% of the project. Be careful, that little 2% stretch could become their sole focus, taking their attention away from the 98% where you are killing it. BE CARFUL!