The following images are all made in "B" mode, which means open shutter for many minutes. My older cameras after 2009 still exhibited many hot pixels when exposing more than 7-10 minutes , especially the EOS 7D being the worst, followed by EOS 5D. Also the excellent EOS 6D got hot pixels, while the EOS 1D Mark IV was very well behaved (best of the aforementioned cameras)

However, i believe that i turned off the dark-frame exposures (I didn't really keep track on when i used it, and times when i didn't). Most of the time, I didn't engage the dark frame exposure (in order to eliminate hot pixels). What is a dark frame exposure; the camera takes a second (dark/black) shot, which then only makes the hot pixels visible - and subtract them from the original RAW file. (You don't see that dark-frame as a separate image).

However, you can take a dark frame shot yourself, with the same exposure but keep a lid over the lens. Then you can use this file, in order to subtract the hot pixels manually from the photo (later in Photoshop). Comes in handy, if you know that you will take every shot with a 15 minutes exposure. Then you don't need to wait another 15 minutes for every new shot.

Hot pixels in post ?

Frankly - I don't know how to eliminate excessive hot pixels in post processing (e.g. Hot pixels which are already present in the original file, and without having a dark frame image file). I would have to investigate that. The Photoshop feature (RAW plug-in) does have a dust removal function - but it only works on those blurry dark spots you get from a dirty sensor. Hot pixels are not eliminated).

Olympus OM-1 + "B" longtime exposure

In the Olympus OM-1, when i use the "B" longtime exposure setting, locking the shutter in the open position - and let's say i take a 15 minutes shot - then the camera makes another 15 minute "dark-frame" exposure, in order to (successfully) eliminate the hot pixels. I don't know if this setting (e.g dark frame) can be disabled - I have not checked that out yet. In theory, i am sure you can disable it...

When the Olympus OM-1 is in "Live Comp" mode

the camera isn't taking any additional dark-frame exposure. So, you don't have to wait twice the time, after the main exposure has been performed.