Thanks for the help everyone 
For the little time I will have with the smaller one (despite hating to waste!) I might just get on with changing it every two days!
This probably brings me on to a new question though …
3) If you’re due to change your infusion set and still have a healthy amount of insulin left in the reservoir, is it safe / wise to inject that back into the bottle so as not to waste it?
I probably sound like some sort of freak don’t I