There is every releavance to how a team is playing now with a team that has been together for the past 4-5 years, since it gives the sample space for the SAME TEAM for an extended period of time.
You can either define 'current' as instantaneous - which means everyone who isnt playing are all at zero, or you can take it to mean how good a team is, based on an established track record. And a team with an established track record, where it does well for 4 years stands in atleast very close to a team that has done very well for the past 2 years, with a lotta minnows thrown in.
That is, if you are talkin about how good a team is. How good one is playing 'currently' is subject to change based on the very next session or two in test cricket. When we talk about form, its very much like instantaneous velocity- it can change the very next second ( or session). When we are talkin about how good a team is, we are essentially talking much like average velocity. It is just that bloody simple!
I guess logic doesnt really work on this site.