Hi kangoo, you can easily change cannula or tubing or reservoir independently, they don't tell you this as they like you to change all at once so you use more consumables i.e. more money for them!! Poor diabetic pumpers in USA who pretty much have to pay for it all themselves, re-use consumables as much as possible, often to unhygienic levels, but it got me thinking and researching re-use. I now change my cannula every 3-5 days, tubing about every 10 days (there's no reason why you can't use tubing for months unless it's been in direct sunlight, which it shouldn't have been as it degrades the plastic...but it's constantly being flushed through with fresh insulin), and my reservoirs last me about 5 days BUT I do at least one refill of each reservoir. Not officially recommended but I can't see why not, having thoroughly looked into the subject and given it a lot of due care and consideration, and it saves NHS money (~£20 per reservoir!) and plastic waste! It's really quite shocking how the poor Americans are pushed to such extreme re-use for months and even years, and what I do is minor compared with some of them. I'm not saying this is suitable for everyone, but could be something to consider - refilling a reservoir. It still means you'd have to faff around with putting insulin in a reservoir every 2-3 days, whether it's a fresh one or refill though. But I agree with someone above that when you go on a pump, your total insulin needs are likely to be much reduced, so you may not need to change/refill every 2 days.
Best of luck with it all!