I think most people would be ok with reasonable loss of precision over very long time like with RRD.
LTS (long term statistics) are never deleted.
What I meant is long term for all sensors.
For what I’ve seen, it’s 10 days by default.
But if you tell recorder to record more, home assistant crawls.
Domoticz for example is able to record months of data without problems, but you loose precision.
That is a limitation of the database type HA uses. There are some other database types that home assistant could change to that would support this. e.g.
I know there are alternatives, but they don’t seem to be supported, and no data migration… 
Yes that is why I said:
It’s a big architectural change though.
you can add Long Term Statistics (LTS as tom_l calls it) to any entity
It will add a record pr hour with state/min/max whatever according to type of sensor:
Some integrations add this by defining state-class themselves
for others you can add state class as customization,
See sample where i add LTS to a command-line sensor, where command-line is not “origianlly” complying with state_class, but I add it through customize
So I believe that this WTH is already fulfilled ?