How much playtime?

Hi, new poster here.  My daughter got a ferret about a year ago, and a
couple of months later, we were given another, so now there are two.
As we had never met anyone who kept ferrets before, we have been
playing it by ear.  Each ferret has a cage, aproximately 1.5x2x2 ft
in, we had to keep them separated at first because the male would play
too hard with the female and we didn't feel she should be harrassed
all the time.  Both are up to date on shots, are fed Iams Kitten food
and whatever 'people food' they like (as long as it's healthy for
them).  Their cages are kept clean and we try to rotate toys so they
don't get too bored.

The problem?  I think they need more time out of the cages and more
time to roam.  Currently they are only out for one hour a day, and are
sometimes put in one cage together now that they play nicely together.

These little critters have given me such pleasure, I really want them
to have an exceptionally happy life.  Our house is small, and people
are always coming in and out, so we have to lock the doors when the
ferrets are out.  The female is a little escape artist and has gotten
out several times - once she even stopped traffic on a busy nearby
street!  Luckily a super-good-semaritan found her and took her to the
local pound, so we could claim her.

I want both ferrets to have good lives, but a single hour a day out to
play seems like way too little to me.  Should they have an outdoor
run?  My husband says he'll build one if we figure out how it should
be done correctly.  I'd like to have a little 'ferret-door' to the
outdoor pen, and keep them both in a larger cage inside so they have
more room to roam and more things to do.  But our vet says that
ferrets aren't smart enough to come in out of bad weather due to 'too
much domesticity'.  He says we'd be killing the ferrets if we tried to
build them an outdoor pen.

~Shelly~