I think it's a personal opinion. I personally have mixed feelings about it.
As you can see by my sig, I've done this twice. Actually the 90 and the 04 are daily drivers for me and my wife (that is my excuse).
But you know how it is with Mustangs. The wife's daily driver has a mod list a mile long (seriously, it has almost the whole aftermarket thrown at it), and my 04 already has a few mods, only after about 2 months of ownership. All this has taken money away from the 68, which is crying for paint, among a few other things. It is VERY hard for me to mod/restomod 3 cars at the same time.
I feel very guilty sometimes, like I neglected my 68. But it never fails that I always get renewed interest in the 68, like I have the last few weeks. It's my baby, its the car that taught me how to work on cars. It's irreplaceable, it will be with my wife and I through the rest of our lives.
The 90 and 04 are nice cars and fun to drive in their own way, but there is just no feeling that compares to cranking the windows down, and taking the classic Mustang for a cruise on some backroads on a summer day. Talk about stress relief!
I could go on and on, but I guess I'm done rambling for now.l