At the 2004 Senior Open at Bellerive CC, about 1/3 of the players carried a 7-wood in their bag. Quite a few carried 1 - 3 - 5 - 7. This was right before the "explosion" in the use of hybrids.
The Darryl Survey Co. polled golfers in 2004 and found that only 7% of golfer carried hybrids. By 2007, it was more than 30%.
Two years go, I went from / 3W + 5W / to / Tour Edge XRail 4W + 7W (21*)/. The extra couple degrees of loft in both clubs really helps out. Golf Digest reported on testing which showed the average golfer hits a 4W more reliably than a 3W - and sometimes farther.
7W and 4H? I carry both. The 4H bridges the distance between my 7W and 4i.
The 7W most often overlaps in performance with the 3H. A 3H would have a stronger loft (19* or so), with a shorter shaft. I actually have a 3H which would replace the 7W in the bag in the fall when the rough is thinner and the winds are higher.
The 7W has become my "go to" club. It comes out of medium rough better than the 4H, can come in soft from 200 yds., and can be used off the tee on short par 4s.
BTW, I'm older, but I'm not feeble. @joekelly, what is your time in the 3-mile run?