The time it’s gained doesn’t matter, but I can definitely second your experiences, I usually get radioactivity as my fourth or fifth mutation, and it won’t go away until I’ve removed literally every mutation I have, which is quite annoying when you’re still mutating.
The only way to get a combination of good mutations is to have Robust Genetics, and then stockpile mutagens/purifiers and just try a bunch of times (Or savescum, but then you might as well just Debug it).
Alternative: Be Ridiculous Lucky™
One thing I’d like to see is a machine or facility that can allow you to target a specific mutation with a purifier, failure injuring you, breaking the machine and arcing lightning everywhere, irradiating the entire area, or mutating you even more, in order of probability of occurrence. Highly dependent on your skills, you would probably want high intelligence and 7-8 science/first aid for a high chance of success.[/quote]
Huh. Might be some way to modify the CBM-installer whenever that gets seriously hammered out–have it go in and purify/remove the mutation in similar fashion to installing a CBM.