I've started on my second jar of the FC test powder, I am near the end of the pH test reagent, I am on my second bottle of CYA reagent. I went through the CYA pretty fast as I was adjusting it for awhile, trying to reduce. Started the first kit in April of last year.
My CYA was in 60 ml bottles and now that I've looked I see that I have emptied 3 of them, plus 4 oz from the big bottle. I have also emptied 30 ml of R-0871, and the powder for FC test. Most of the other bottles are at 30% left or more. I will guess that at the start of next season, at 2yrs on the kit, I will probably need to replace most of those.
So, were I going to suggest how much of extras you might need to make it a full 2 years... total 3 - 30 ml bottles R-0871, total 2 vials of FC test powder, 2 - 8 oz bottle of CYA reagent (original bottles included were about 2 oz or 60 ml, 2 included).
I read that the kits now have larger bottles included than I got in mine so you need to look at the totals I've posted there.
I've reordered stuff 2 times, each time adding a few things I did not need just to justify the shipping, each order was something like $20 to $25 IIRC. I think that last order will probably take me into the 24th month so I'll guess the 2 year cost will be $120 total with shipping and all. Call it $60 a year for test supplies.
The strips I had were $29 for 100 and that might last a year, so though this is more expensive, the tests are so very much better that I am sure that I have avoided buying hundreds of dollars worth of junk to clear up a green or cloudy pool. I've never bought algaecide or flocculant or clarifier or any of those other things you see at the pool store and my pool is perfect... as long as I test on time and add what it needs when it needs it.
The average pool owner, who doesn't have anything dramatic happen, can get two to three years out of the TF-100. Depending on your situation, you might use up one other another of the reagents more quickly and need to re-fill that particular one sooner than that. A baquacil conversion, or several bouts with algae will use up the FAS-DPD reagents. High CH levels can use up the CH reagents. And so on.