"locking in" FTP gain

After general build mid volume and speciality road race mid volume plans I’ve got a pretty nice increase in ftp. I don’t feel that fatigued and I have 4 more weeks before my August fully off the bike for family holiday. Do I do a 40K TT plan with plenty of SS training to “lock in that new ftp” Is there any science to that concept of locking in an ftp? Or do I go to the crit speciality plan which does replicate my “event” (Saturday park chain gang smash fest)?

Not entirely sure what you mean, but a month of training will mean some degree of detraining as
your body thinks maybe you’ve given up this biking malarkey and it can focus resources elsewhere.

If you mean maintaining a bike fitness level, then yes you can do that, the maintenance plans should suit and be easy to sneak in if there a gym bike in your hotel.

Sometimes if taking just a week off, we go extra hard the previous week because we’re planning on getting extra recovery…but I think a month is a bit beyond that.

Oh sorry, what I meant was what should I be doing for the next 4 weeks before my annual August off?

From memory there are specific TR plans for that, but I can’t remember their names.
Don’t think you can ‘lock it in’ though. You still need to do something even if you’re happy with a plateau.
My experience is that it’s either going up or down & cyclical ups/downs are unavoidable. I don’t think I’ve ever achieved “plateau”, although I’ve never tried one of the TR maintenance plans.

Even if there is no locking in a FTP, there is the phenomenon where it doesn’t take you as long to reach a past FTP even after detraining, right?

Locking in is not really possible. It implies that you can hold a value. While that maybe true in part, the reality is that fitness is usually rising or falling. It’s seldom stable.

To the goal, extending a fitness peak is often done by repeating the final 2 to 4 weeks from a Specialty phase.

Another option is the “Maintenance” plans, from the Enthusiast section.
https://www.trainerroad.com/cycling/plans/category/23-enthusiast

Interesting. I have 4 weeks before my end of season so I’ll just repeat the final 3 weeks of my speciality plan that I’m on now and just see how I feel in the last week.