what is your indicator? when do you know time is up and when they need service. I am still kind of on the fence as to weather or not to get my centurion ironman BB hs and hubs serviced, they roll and spin perfectly smooth and quiet but i dont know when they were last done, and its kind of a lot of $ to throw down for something that might be fine for a few more years, any thoughts?

External bearing cartridge BB for me, so no need to worry in regards to servicing.

Hubs, I probably do them once every 9-12 months. I do check them regularly though, and I'll do them if they feel a bit dry or gritty, or if I've recently ridden in heavy rain.

Same with the headset.

If they're fine for now, and cost is a concern, they probably could go for a bit longer while you save up the funds. But in the end, it's preventative maintenance, and peace of mind, knowing they've been done and not having to guess if they're okay or not.

It's too late when it's grinding, as this indicates that your bearing races are pitted.
If you don't know when it was last serviced, you might as well service it, since the grease does dry up over time, and despite feeling 'smooth' the grease can be completely contaminated or missing entirely.

I've encountered several pedals, hubs and headsets where it was claimed to be 'smooth' when in fact it was not under closer inspection.

It's not too hard to service the bearings yourself. The tools would be something like $30.
https://www.parktool.com/repair/readhowto.asp?id=127
https://www.parktool.com/repair/readhowto.asp?id=105

yea sounds good, the bike is from 87 and i love the thing to death(going over the bearings is the only thing i have not yet done since i got it a few months ago) so im gonna take it in to the LBS this time(have been "practicing" on my old murray 10 speed crap bike, so by the time its up for another service ill probably do it myself

oh and just curious, what does your LBS charge for this? i think i remember mine saying like 25 per hub, would BB and HS be about the same?

I'm guessing you have loose ball bb/threaded loose ball headsets. In which case BB's should be $20-$40 and headset should be around the same. Parts extra obviously.

Annually with a complete tuneup.

If you have a loose ball cup and cone BB you will not find replacement axles, so Annually, every spring is a Good Idea,

you will have to replace it with a cartridge BB if the spindle gets or has Pits in it,
spare axles have been discontinued a long time ago .

NB you can improve sealing by stacking O rings on the axle to press against the outside of the Cups , before you
put the arms back on, how many depends on axle length between the 2.