If you don't focus on buying back exactly as much sats at the exact same rate, then it's not so cumbersome. I know I spend about x amount per month + I know I will got to a conference and spend some, then when I see a drop, I stacks enough to cover that + some margin. If I had an unplanned sats spend, small amount is ok, larger I also try to buy back in the next 2-3 weeks as much sats or more if I can afford. If you do that you should be able to spend sats without bothering about the rate as you always buy back a bit more and on average it should more or less be the same rate unless it's during one of the short and rare parabolic phase where you might plan differently.

Eventually we will do the opposite, as it will be more profitable to hold everything in BTC and keep only a small amount in fiat for daily purchases, then you sell when you need to pay a bill or something. Some service will allow you t pay bill in BTC directly and the bill is settled in fiat for you in the background, until everyone accept BTC.
When you have only one month of budget or less in fiat on your bank account and that it's a fraction of your BTC holding, you are doing it right. 

 > When you have only one month of budget or less in fiat on your bank account and that it's a fraction of your BTC holding, you are doing it right.

Nice metric! 😃 

Btw, how do you deal with tax reporting of purchases made with BTC? 

 I'm in Switzerland, no capital gain tax, nothing to report. 

 Sweet!
I'm not so lucky ...