I've generally adopted the tactic described above, I make up a job I'd like to do then I justify buying the tools for the job I might do. Case in point today was a £150 trip to screwfix when I could have used a hammer, nails and punch to put the architrave up, the problem was I'd already bought a nail gun and the compressor I'd borrowed didn't work properly, so of course I "had" to go and buy a new one that being said fitting architrave with the nail gun is so much more fun