I've never used the LTR myself, so I don't know if this information will be useful.
Coming from recently playing the Criminal Career and how many days you get off with that career anyway, this LTR sounds terrible.
When I was playing a criminal, my Sim's work performance never went down. On her days off, it would be static. - However, I didn't have this LTR, so that might make a difference.
This is what I find when checking out the Sims Wiki
https://sims.fandom.com/wiki/Lifetime_rewardVacationer
Feel free to take the occasional day off. Nobody at work will notice!
15,000 = Teen
When Sims with this Lifetime Reward take days off, their work performance bar will go down much slower than usual. When they are home, they will not get paid for doing their job.