Rulers -- only if they are damaged. Although I'm really tempted to try those new
Guidelines4Quilting rulers.
Cutting Mats -- When worn. Every 3-5 years depending on use. I do use both sides.
Rotary cutters - haven't had to replace one yet
Rotary blades -- with every new quilt, no exceptions! Sooner if there are any issues cutting.
Pins -- when they bend. I use silk pins, so I end up buying a new 100 pack every other year.
Needles -- when I start piecing, when I start quilting, or if it sounds bad (max of every 8 hours)
Chairs -- haven't needed to. I guess every 40-50 years (mine is 20 years old & still as good as Day 1)
Sewing Machines -- goes in for cleaning once a year, service every few years; don't see need to replace a machine, but I only have a Bernina & an old Singer so they're basically all metal parts
Scissors -- never. I do send them to be sharpened by Gingher 1-2x/year
Seam Rippers -- not as often as I should. Usually only when I lose one -- every 5-7 years.