Perhaps his Mrs is secretly off with a toy boy and she'll give him the elbow?
Could be the case, tho given his OHs situation unlikely
However:
"8yrs. Im a regular punter, anywhere from 3-8 times a month"
Thats an average of 5.5 a month * 12 * 8 = a grand total of 528
Much more likely is that unbeknown to the OP it didn't take long for the OH to become aware of his activities
There are only so many times that someone can go to B&Q for a peruse

A suspicion which develops over time into something more concrete
Blokes have a short memory span however women are like elephants
I would suggest, unless she is completely clueless, that she knows full well when he goes to get his tanks emptied
A grumpy individual around the house goes out [to B&Q, again

] & on his return skips down the drive humming 'zippity doo dah ... '
& the OH prefers this set-up [like sooo many couples] as it preserves the partner / relationship equilibrium
As long as its not made obvious to the OH
& much more importantly that the OHs girly friends don't clock it otherwise this is where problems can really start
"what you let him do that & don't say or do anything"
The peer pressure ramps up & the outcome is v.unlikely to be +ve
I've seen it happen to one of my mates
Under the radar all fine
The OHs friends find out [a reasonable chance they are in the same / similar position]
& WW3 beckons as suddenly the girly friends think that there is a clear & present danger to their own supposedly harmonious household
Especially when they are comfortable financially
Forever ago since they needed to have a job its pilates & lunches nice car nice house holidays cleaner etc
They have to stop this in its tracks, not for their supposed friend but for themselves
Best that the bloke gets himself an iron dome defence system as the missiles will be arriving
So for the OP as in Black Adder 'deny everything'