Loads of 135 mostly C41 , some BW , E6 some 120 roll . Years of it. !!!
In my initial catch-up scanning, I did approximately 150 rolls of 135, roughly half black and white, half C41, with a few E6 and a few Kodachrome as well (there may possibly have been some pre-C41 stock in there too; it dated from the late 60s to the early naughties). I tackled it as a long term project, maybe one or two rolls an evening. ISTR we were watching a lot of commercial TV at the time, and I'd nip upstairs in the commercial breaks and scan another couple of frames. As you can guess, it took the best part of a year to get through that backlog. Some packets ended up being scanned several times, if they were important subjects and I learned a bit more about handling colour, dust spotting etc after the initial scan.
I think you might get better throughput on an Epson V500 than on my Plustek 7500i, as the latter scans one frame at a time with manual advance, while the Epson lets you scan multiple frames. OTOH the Epson 35mm holders are pretty awful if you've got curly film. I found that although most of the cut film was OK, having spent decades flat, some screwed up corkscrew fashion, with a curl fighting against the flattening!
By far the worst issue I found was the appallingly casual treatment (by me, I assume) of older negatives. Usually not sleeved, jammed together in the flap of an envelope. Recently I started filling in some gaps I found. One film, documenting the period around the birth of my son, had strips glued to the side by whoever did some prints; I suppose they were for ease of handling. I had to get them off so the strips could go into the film holder... and in the process tore the first known negative of my son across the top corner!
For the initial set, I too had to decide between outsourcing and doing it myself. One thing that moved me towards the latter was that the cost of outsourcing meant I would have to be selective, which would be difficult enough when viewing negatives. But I though extracting film strips and sending them off in bulk would result in masses of images that were hard to associate with anything, and a massive filing problem. Doing it myself, I was able to use clues written on the envelopes, dates, film stock etc to help. I try (now but not always then) to identify the year, approximate date or sequence within the year, film stock, camera if known, place or event, in the file name for each envelope of film.
I started out using Silverfast 6 SE that came with my scanner, but eventually changed to Vuescan Pro, which quite a few people here use. However others here seem quite happy with Epson Scan, so you could experiment with that at first, at least.
Slides could be a problem as they were often extract from their original sequence to be shown in projected slideshows. For some Agfa and Fuji slides in plastic mounts there were very few clues as to what was what. Kodachrome and Ektachrome tended to be in nice cardboard mounts that were more likely to have clues written on them. If not I found the sequence numbers and their colour (red or grey) really useful.
By the way, I found this scanning an immensely rewarding process, during which I discovered things from my past that I had completely forgotten about. I also found the internet in general, and this forum in particular, very useful in identifying locations. When all else fails, load up foogle maps and study the shapes of the horizons from street view or panoramio pics!
So, good luck, and do please share a few of the results with us, whichever way you go.