I bought a spare enlarger. Of course, if it is rare and/or expensive that may not be practical, but L1200's were being sold for 100-150 GBP or so here at the time. I also managed to buy a spare power supply for my AC1200 on the auction site recently (thanks to a tip-off) for peanuts so I have a spare should my existing one fail.
It's often worth keeping an eye on the auction site in case something useful comes up for little money that you can store until needed, or to be sold on later with or without the enlarger.
Good luck, Bob.