What method would be the most convenient for storing over a hundred hours of footage? Digital looks convenient, but I think backing up that much video can be expensive. My inspiration is Jonas Mekas, who recorded a lot of (mostly) home movies on film, and I'm wondering if film could hold any advantages for me. My biggest concerns are the cost and durability of storage.
My general advice is not to worry too much about storage when you are starting. I gathered from the comments that those 100-something hours of video will accumulate over life and this allows to upgrade storage solutions as you go.
Normally you record, edit, probably import other assets, record sound or music, etc. Then you export a video master file (for the archive and to create new delivery files from) and a number of delivery formats right away to publish the video.
The actual capacity you need will also depend on what you keep: all source material or just the end result, like a high-quality masters and maybe a few delivery formats. If you also want to keep all source video files, storage needs depend on what the camera can produce. Cameras targeted for professionals use storage-hungry RAW formats whereas consumer-oriented cameras usually use compressed formats with low storage needs. You will probably start with the latter and won't produce huge files for quite a while.
Since you said you make short videos, I think it's sufficient to buy a 8 TByte disk and it will be enough for a long time. After about 5 or max 10 years, the disk will reach its end of life and can be replaced by a larger one that surely will be cheaper than it is today. For fast editing you can use an SSD where your operating system and video software is installed and where you put the source material for the current video you're editing. So the SSD doesn't have to be that big.
Regarding backups, it's safer to keep at least 2 copies besides the original. For fast access it's best to have a local backup on an external harddisk. To protect yourself against catastrophies, put another copy at a different geographical place, like a friend's house or upload it to a datacenter designed for backups/archiving needs. For a service like Wasabi you'd pay 6 USD per month for 1 TByte. If you use external harddisks they too have to be replaced over time as they degrade. However, since they are used less often, you can replace them at longer intervals. It's good if your backup program can use checksums to check if files on the backup medium have changed (because of bit flips or block read errors). When this happens replace the disk and re-generate a fresh backup using the original or the other backup copy.
Tape backups are another option. If handled well, tapes should stay intact for about 30 years. Tapes are rather cheap, but tape drives not so much. I'd say tape storage makes not much sense in your case since your storage needs will grow slowly over time and you benefit from the cost degredation of harddisks. It has become harder to find a service for tape backups as the trend seems to go to cloud storage solutions.
It's probably worth to re-evaluate backup strategies every 5 to 10 years for cheaper or better solutions. For small projects/businesses it's often best to invest only in the capacity you need for the time being and the next few years and not plan for decades ahead.
That said, filming digitally with a good backup plan should fulfill your cost, durability and convenience requirements.
To give you a glimpse on analog filming: A 400 ft roll of 35mm cost about 300 USD, or 16mm costs 200 USD, Super-8 is sold in small quantities and is therefore even pricier. Those 400ft rolls only enable you to film for a few minutes. Then there are costs for development, and costs for scanning if you want to edit it digitally - and this means you produce digital files anyway and those aren't small either. Finally, you do master prints and have to store all of them in some controlled environment. If treated well the durability is much greater than anything digital. But the archive space costs you. All this is why you won't be able to save money when working with film and it's much less convenient. It's also getting harder to find services that develop and scan the film for you.
Still, it might be fun to make a short analog movie but it would be a costly choice when dealing with large amounts of material.