Wise? That very much depends on the engine. What is a bit past? What are you doing to monitor your engine health? What is your plan? What are you basing your plan on?
Calendar age since the last overhaul?
What do the oil filters looks like?
Boroscope showing anything?
Anything popping up on the oil monitoring?
Engine producing full power?
But one of those snowmobile engines with a coolant system and a gear box and a dog clutch? No way. There’s just too much to go wrong.
Provided that you know the engine's history and maintenance has been completed by a competent and knowledgeable Rotax certified technician. The engine could run a few hundred extra hours past TBO. These engines are "on condition" due to the fact that they are uncertified here in Canada. So TBO is only a recommendation from the manufacturer.
Also, if the decision is made to remove the engine in question and send it to Rotech in Vernon B.C., they will sell you a new one. Rotax has had several updates on their engines in the past several years. Crankcase being one of them.