You can use interval shooting and combine the images. This is inconvenient, but I've done it a bit with adapted lenses (where the maximum time per shot is 2 seconds). Of course, this only works if gaps in the exposure are no problem.
If you want JPEG you can even get the camera to combine them (multiple exposure mode), but I want RAW.
There are doubt a lot of programs you can use for this, but the ones I found all seem to want JPEGs, which means I get to develop them first and then combine them. I wanted to combine the RAWs and then develop them as if it really had been a longer exposure, so I wrote my own.
dngcombine isn't particularly general, but it does work on the files produced by the Q. If you are not a command line person it might not be for you though.
If you really want it, you could disassemble your Q and put a locking switch on the shutter release contacts. (Assuming bulb will go that long, I've never tried it.)