[Closed] bit of advice - training for endurance events

Hi,

I've entered the Glentress7 solo, it's at the start of June, so just under 4 months away.
Trouble is that with time constraints - work and busy kids, I don't have time to do much training, and certainly very few longer rides.
I end up commuting ~3 days per week. If road then 40k round trip with ~400m climbing, if off road 40k with ~800m climbing.
So most of my riding is in 40 mins to 70 mins stints.

Any advice on how to translate this into some decent endurance training?

I did the race last year and was a bit disappointed with 7 laps, mainly due to dehydration and cramp. I have ridden for 10+ hours before, so that is not new to me.