Wasting insulin?

[heasandford]

I am sure there have been posts on this before, but I am returning to the wonderful forum to ask their opinions!
I don't seem to have much of a pattern to my life these days. (lucky retiree!) In order to manage my pump, I decided to change cannula every 3 days then cannula and cartridge together every 6 days. On some levels this works - I tend to remember things need changing on the right day, I change at the same time after I've showered in the morning, there is no pattern of poor results attributable to this. However, depending on what I've been doing - walking exercise, eating out, entertainment etc - then the amount of insulin in the discarded cartridge can be more than I'd like.
I do try to balance the amount of insulin I load in order to last 6 days. But I don't really like the idea of being 'caught short' when out with insufficient insulin in the pump - has anyone got any ideas?

 

[Radders]

I can't avoid wasting it unfortunately as I only use less than 600 units a month, so I always end up throwing away 4ml out of every vial. I suspect most of the cost of producing the insulin is fixed costs anyway so the cost of one unit is probably insignificant.