The 2v industrial batteres are made for true deep cycle performance. They are typically rated (not that battery manufacturers’ lab tests mean much in the real world) for 8000 cycles @ 20% discharge and 3000 cycles @ 50% discharge. The standby life is listed as 20+ years.
In practice they make an excellent house bank, with a well proven long cycle life. They should be considered more often, especially for boats with solar
as the primary charge source.
The lack of redundancy can be managed by choosing batteries with half the desired capacity. This means wiring
two sets of six batteries. The 2v spiral wound batteries are not modified car batteries. The design goal places a high premium on reliability
and they seem to have a very low unexpected failure rate so this is arguably overkill.