As with all moving parts involving oil the single most important factor in keeping them in perfect nick is removing dirt and grit. No, not the stuff you can see easily that you wipe off with a cloth but that of minute proportions that can easily turn the oil into a fine grinding paste that works away on your spindle and bearing EVERY time you spin the reel.
Anyone who has any working knowledge of needle and roller bearings, particularly those of minute size will know what I'm talking about.......
As an (retired and boring !) engineer I cannot stress enough the importance of keeping moving parts of your reel scrupulously clean which, as far as I'm concerned means opening the reel once a week to check for said grime and EVERY time when it's been subjected to dust laden dust particles carried via rain etc.
The use of a 'kept for the job' soft cloth and the suggested sewing machine oil on a regular basis is a very good habit to have, as is the use of a proper bag in which to keep the reel !! Absolutely pointless to sling your precious c'pin reel into the tackle bag without protection, which, by definition is dust laden from many fishing trips
It'd worth mentioning that just because the reel spindle looks okay ( covered in a film of oil ) doesn't mean to say that it is okay. Any oil looking slightly 'grey' in colour, or in fact any other colour than the standard oil colour probably means the oil has mixed with some other substance. (Check you car engine oil a month or two after servicing to see the colour change.........not quite the same thing but you know what I mean!
It only takes a minute or two to wipe the moving parts and re oil although I'm not suggesting this needs to be done after every use UNLESS it's been used in really adverse conditions.
My own centrepins are all over 50 years old (one ore two a lot more) and all are still in perfect working condition even though some are used on a weekly basis, in winter summer, in rain and everything in between....
Some might say all of this is a little OTT, and they may well be correct to some extent, but IMHO total care of your gear means it is always reliable and ready to go although as my wife would probably tell you I am a very 'clean' person, sometimes to the extreme and it's not unusual to hear "you're not cleaning your fishing tackle AGAIN, are you"??
Anyway, although I like to lean toward 'perfect' rather than ' near enough is good enough'......I appreciate others may have a different view of clean, though...........................................