I have burned some rescue discs (MultibootDVD) and a test CDDA-CQ for a day in/at swimming pool.
I backup video, work files, photos etc. I use BD media about half the time nowadays. Also, I burnt some pork chops on the grill the other day.
On DVDs, I do some redundant backups of typed documents and work.
I also run PortableApps.
Most of my burns are movies and series I recorded on my DVB-S(2)-Receivers. In the past I also used DVD-/HDD-recorders from JVC, Panasonic and Pioneer, but the quality is much better with DVB-S(2). And these recordings I can cut easily on my PCs and burn to DVD/BD
On my work I burn many versions of Operating Systems for installing/updating Software-Test-PCs and Software for tests also.
CD-Rs I use very rare