Nope. People turn them off all the time, it’s even part of the software update process. Just plug it in to s power source and hold the button for line 30 seconds, until you see the shutting down dialog. The only problem with turning it off is that is erases all short-term memory things (insulin on board, time remaining on boluses, amount of insulin in the cartridge, etc…) and will force you to go through the fill cartridge process. None of that should matter to you, though. That’s only really an issue if you try to shut it down for a few hours.
Have you actually tried the apidra in the t:slim, though? It’s a mixed bag of chips. Some using report occlusion issues, but it works fine for others. Maybe give it a shot if you haven’t tried it yet?
I’m guessing you don’t have spare supplies built up yet, and don’t want to risk them on a setup that doesn’t work. Personally, I’d refill a used cartridge with just like a days worth of Apidra to see how it behaves. If no problems, try again with 2 days worth in a used cartridge, then 3. I don’t think the infusion sets are going bad with these blockages. It’s more like if the insulin crystalizes, it gets stuck in the connection needle, which is finer than the cannula.