I always enjoy seeing Guard aircraft as I travel through airports around the country.
Even at a distance, you can see the great pride and attention to detail the crews take in their older aircraft.
It's been a long time since the Guard flew "Older aircraft". The average KC-135 in Guard units is only 1 year older than tha average active duty bird, 47.7 46.6 years respectively. The Guard C-130s are actually younger on average than their Active Duty counterparts, 20.9 verses 32.9. Average active duty F-15C/D is 24.7 years old, average Guard F-15 is 29.7 years old. For F-16s it is 17.9 years for the active duty fleet, 20.1 years for the Guard fleet.
For the F-15s some of that age difference reflects the mission differences. Guard F-15s are almost exclusively in Air Defence mission (i.e. guarding the US Mainland, plus Alaska & Hawaii against foreign bomber threat, (and the odd Muzzie terrorist), while the active duty fleet is in Tactical fighter units, tasked go against an adversaries own fighter aircraft, a somewhat more demanding mission in terms of needed to have the "latest and greatest". (Data on ages are as of Sept. 30, 2008)