Refill smoke fluid run time?

Smoke time varies way too much to set a time frame before adding more fluid.  The amount of drops of smoke fluid added makes a big difference on run time.  The best gauge is to simply add more fluid when the smoke coming from the stack gets light.  Run time also depends if you have your smoke unit set on low, medium or high if it is adjustable. The time an engine sits also has a bearing, as fluid in the smoke unit will evaporate out.  I limit this from happening by covering the smoke stack with aluminum foil.  I have found that I can triple my run time by using this method after shutting down an engine.

Thank you for the reply.  So As long as there is some smoke coming out there is no risk of damaging the smoke unit?  And I should see see light smoke before adding more as to not overfill. 

When the smoke volume falls off very noticeably, I add smoke fluid.  If you have good smoke, let it run until the smoke volume is at least about half of when you first filled it.  Also, different locomotives will have different run times.  I have some that seems to drink the stuff in gallons, and others that will run a lot longer before a refill is needed.

It will also depend on how many smoke until the locomotive has. My MTH Centipede has 4 smoke units.

Thank you for all your replies. Very helpful and now I have a good idea what to look for without over worrying.  

See the following videos by Laidoffsick, very helpful:

https://www.youtube.com/watch?v=WRcpFRtA6IY

https://www.youtube.com/watch?v=1asUWbJtfok

I have been experimenting with 1 drop of fluid for each minute of run time with 10-15 minutes between refills; but, I have not taken apart a smoke unit to verify this; my objective is to prevent burning the wick.

An hour?  No way. It depends on the setting but IMO 5-10 minutes max. 10 minutes is probably pushing it especially if its set on high.

Thank you RickM46 for sending the videos from Laidoffsick.  Those explain a lot!!  

There is also something else I keep in mind when counting the drops from a Lionel dropper: some of it goes to just wetting the funnel first.  Ain't smoke units fun!!  Saving grace: easy to rebuild; Lionel has parts; done the one in my Big Boy.