Duration of sweetspot intervals?

Hi all, am 2 months into TR & loving it. Training for an 8 day 1118 mile ride in March '21. Got (what I believe is) a decent base, after mostly Z2 3700miles this year.

I completed SSBHV2 at 243 ftp & added additional 4 weeks @ 248ftp & coping just fine. I did a 14hr 172mile MTB ride 2 days ago, about 10hrs in Z2 & feeling great. Judging by intervals.icu & Garmin I should be recovered today already. I’ve been told that my ftp setting might be too low.

I’ve got 2 weeks to wrap up the last 3 weeks of SSBHV before moving onto SBPHV due to travel. I’ll use the travel week as recovery before going into SBPHV.

Question: do I

  1. double up each scheduled workouts consecutively - did this twice & loved spending 40min in SS
  2. do 2 x SS workouts per day on alternative days to allow recovery
  3. substitute scheduled for longer SS duration alternatives - which are these alternatives

I’m leaning towards option 3 but just need to find the alternatives & could do with some advice as to whether I’m getting ahead of myself.

Cheers and thanks in advance