I'm actually really shocked that more people don't get to know the inside of their reels more intimately.
All of my reels, fly, bait, c-pin etc. get torn apart once a year if not more in a season. Most reels are very simple to maintain and in todays world of youtube it is even easier to work on them.
All reels will collect sand, dirt etc. regardless on how careful you are with them. Most require a simple wipe and re lube or oiling, but when doing so remember one ling about grease and oil "a little goes a long way" using too much can and it has caused the reel to not function as smoothly or efficient as it should. You will know right away and the worst that will happen you will need to tare it down again.
My c-pins will get taken apart almost bi weekly if used that often just for a quick wipe and oil on the stem. I use bearing reels so once ever 2 or 3 oiling's the bearings get soaked in an oil bath for an hour or so.
My bait casters which are used mostly throwing spoons will get torn down probably 3 times a year. Once before spoon season and twice during. (if I need to change the line, the reel gets serviced) The first one is a complete tear down, wipe, and re greasing/oil of each component, while the 2 services during the season are usually a simple oiling of the worm gear, and shot of oil with brake cap(s) removed.
My fly reels are very similar to the c-pins with out the bearings. However the lines get a mild soap and warm water bath before the season and the well used lines get the same treatment more often to remove any dirt on them.
2 reels I struggle most with are my sturgeon reels, Penns. I have torn them down once and probably will never do so again. I don't like the springs that pop out in every direction and if memory serves me correctly the drag component's are a pain the my friend. Luckily they only get used approx. 1 day a year now.