Never. Fuck concerts. The last time the security took the cap off my water bottle. The tickets are difficult to get, and the music is too loud. Not to mention the sea of smartphone screens blocking the view!
How big was the show? Local bars are where it's at, can see amazing shows. I haven't been in a while, but used to go see Local H whenever they were on the East Coast. Toadies, islands, white horse, superbob, status green. Found some amazing bands on a whim and $10-20 fee.
For classical music, I used to go every other week, these days I go much more rarely, let's say once every month or even every two months. (But just last week I went to four because there was a festival.) For non-classical acts, I try to catch every performance of the bands I know, local or non-local, and maybe try something new and random just so, which usually amounts to 2-3 concerts a year.
I've been trying to go to a concert, at least local, at least once a quarter. I do buy merch, often vinyl records or T-shirts, but I have hard price limits; I'm not paying more than $50 for a vinyl (unless it's a double) or $35 for a shirt, max, and due to my budget I usually have to limit myself to purchasing only 1 or 2 items per show.
A few a year - currently festivals as my eldest has heavily got I to 'our music's - so I've had to take time off work to take her to slipkot, korn, baby metal, electric callboy, etc.
Depends which acts are on tour in.... Yep, Australia. So last 12 months I went to 6. Work into the mix many of the venues are on the other side of town to me (so week nights are usually off the table unless I must see; Mastodon) and that tix are often very expensive - especially for big names.