Last year - upgrading to an 4040 R/O from a 450 GPD. Now we have enough water.
Over the last 8 years of doing WFP we have had a number of these best decisions; some we agonised over and some we struggled to justify the expense of. But once made became part off the learning curve.
Changing from Unger Teleplus poles to carbon fiber telescopic poles was a major step forward. They were more expensive in those days and we needed to justify the cost.
Purchasing my first Aqua-dapter 2 1/2 years ago was another.
Not all decisions were good ones in hindsight. I bought an SLX 40 to target some higher work, but for one reason and another (mainly health) never focused on that side.
It gets used on a couple of jobs over the year we now have, but hasn't paid for its cost TBH. But if you don't speculate, you will never push forward.