I trained for the DeathRide 3 years ago, before owning a trainer and TrainerRoad. About this time of year I had built up to doing longer outside sweet spot intervals, maybe 15-20 minutes. And then built up to doing 1 hour sweet spot intervals twice a week during May and June. Because my training was outside into a headwind on flat roads, those were really more threshold efforts. Found an earlier post about overall zero-to-hero training experience here:
Not counting this week, you’ve got 15 weeks to train and 1 week taper? So yeah, 6 weeks SSB-HV-2 and then 8 weeks Sustained Power Build sounds like a good plan. Given my prior experience, over time I would substitute longer 30-60 min sweet spot/threshold intervals for the 20 and 30 min jobbers in the plan. I’d also try and do some training rides in the hills/mountains.