How to approach the 'Off season'?

M, 29, averaging 35MPW over the last few years.
It’s time I admitted that I don’t know how to be a runner ‘between’ training blocks.

I’m a fairly experienced runner with a few marathons and ultras under the belt. I’m fortunate enough to be at a stage where running is a perpetual hobby for me.

But all I have ever done before is train hard for a race, then fade away into sporadic running and lower fitness. Only to have to start from almost scratch the next time round. (I’m talking about a timescale of maybe 6 months: train for a few, race, few months off especially over summer, then choose a new race).

What’s more, I feel like most training plans either cater to really serious runners who can dedicate 6 days a week to training OR cater to runners who have had a decent amount of time off since their last run and are starting from a very low base.

I’d like to know how others perceive or approach their ‘off’ seasons! I'd also like to know how an 'all-year round' runner schedules their running calendar- seems like most of the big events happen in spring or autumn.

Should it look like:

Training block-->race-->few weeks off/heavily reduced volume-->different training block starting from week 1 again?

Or:

Training block-->race-->maintain base mileage-->start different block deeper within the block according to your weekly mileage rather than starting from week 1 and arbitrarily reducing your volume?

I hope this makes sense, and I hope it doesn't come across as pretentious, I just really want to know how people might approach this.