Hello @shawnfife hope you are well.
I have a number of athletes in that very range, but also a few that sit around 1h03m to 1h17m at 305-315w ftp. Those athletes have LT1 around 215-225, LBP 245-260 (depending on whether they are about to race or just in training phase) mFTP around 310-335w.
I got there by always training the endurance in the 2-3h range 10-15w below LT1, if it was 4-5h it was LT1 as a ceiling on climbs, goal NP for the ride 165-180w depending on how they feel. The shorter usually road or gravel, the longer road or gravel or mtb.
Training the tempo at 235-250w, so below LBP 15-20w
Some lactate shuttle work just below LBP to just below mFTP, so like 5m 10-20w below mFTP 10m 10-15w below LBP back and forth for periods of time.
There isn’t always a hard workout in the week, I usually do blocks of above for 4-6 weeks, then blocks of harder training for 2 weeks.
I can’t say for sure that the LT1 LBP can’t be pulled up…but I don’t often see that happen.
If you look at an entire season, LBP will fall when volume drops as intensity rises, to bring LBP back up - raise volume, drop intensity, be careful with the races that are chosen.
So I guess I always just push it up.