I think it's the best idea in the world to keep some things similar in design. Someone also mentioned in another thread that we're still using Planes that are 50+ years old. I'd like to point out the F/A-18, which was put into service in 1978, is still in Service today as the F/A-18 Super Hornet.
I think using similar designs brings a continuity between movies and a relate-able experience for viewers. This is something the Prequels really didn't do well (IMO).
The Super Hornet is a different plane, it just happened to borrow heavily from it's parent. That being said, the F/A-18 is still in use by many countries. Australia is waiting on the new JSF's to replace their aging F/A-18's.
Hornet and Super Hornet:
