Around 10 years now!
It started with me thinking modern gaming trends were crap, and remembering how much I liked games in the 90's.
Then there were just a couple of factors that happened to pull together to build up the perfect storm.
An interest in great (mostly japanese) VGM, a deep dive into 90's anime (mostly OVA's) and becoming a fan of CGR on YouTube.
I decided to buy and play a lot of SNES games and got a Saturn with an Action Replay and some japanese games.
The first real STG I played and cleared was Axelay. Really loved Konami's output on the SNES (LET'S ATTACK AGGRESSIVELY). Rayforce (Layer Section) was a big step up in difficulty but I loved it. About half a year after all this I happened upon a place in my town that was a combination of a café, a retro game store and a game center. First Arcade STG I tried was DDP DFKBL and I fell in love with the spectacle. Since then I became a more frequent visitor and eventually happened upon sven666, when he was visiting, and started talking. He learned that I was interested in Garegga (I had listened to the soundtrack on YouTube and thought it was crazy good), so he eventually put it in one of the cabs. Needless to say, it was all downhill from there.
Started buying a lot of arcade PCB's, to the point where I had pretty much all games I was interested in, except for the really expensive ones (only Futari BL was in that category, but I got it for cheap).
Fast forward a lot of years later and there are only very few games I like enough to put the time into or have time to play, coupled with starting a family and needing more moniez, I have sold off most of the games I bought. Total net earnings are around 200-300% given what I payed at the time.
A seemingly ridiculous investment at the time, that actually turned out to be a wise one.
Will continue playing Garegga and Batrider indefinitely!