My most used camera is a 294MM. Before you decide that you need long exposures flats, try a regular short exposure flat and see how it works. You may find that you don’t need a long exposure. And if you can do short exposure flats, then you can use bias frames instead of flat darks. Although, flat darks still work best.
The 294MM has a few issues that affect some cameras. But the one you need to be particularly careful of, is how the camera’s software handles short exposure, then hands off to the imaging software a 1 sec for longer exposures. There is often a lack of linearity at this point. So calibration frames less than 1 second, don’t work properly with exposures of more than 1 sec. When that happens, the flats don’t correct properly. I see that every once in awhile, but not very often, with my camera. I usually use a light panel to do short exposure flats and equal length flat darks. If I have a problem with the flats correcting, then I’ll go back and shoot long exposure flats and flat darks. Out of all the imaging I’ve done this year with that camera, I’ve only had to do that once.
Another thing I’ll mention is how that camera produces pretty ugly flats when used with Ha and Sii filters. That’s due to a poor job of coating the imaging chip. It varies camera to camera, but looks pretty bad with mine. If you notice it, don’t worry, flats will correct it.