NOTE: Speculative until verified.

• A stone houses(walls/windows/doors) perish-ability is 3, making its average decay per tick (3/wall QL).
• A wooden houses(walls/windows/doors) perish-ability is 10, making its average decay per tick (10/wall QL).

  Considering this information…

Assuming a 70 ql stone wall..would mean that wall would last for 2500 days…Clearly an off deed 70 ql stone house will NOT last for 6.8 years increased abandoned decay is 1.5 months…so 45 days as month is defined as 30 days when purchasing upkeep or premium time.

For non-abandoned houses that are off deed the decay rate is (perish-ability/QL) total damage per decay tick.