My questions are what is the R value of the siding, and how long will the vinyl last?

We used Tyvek behind our Crane triple 6. Other insulation was wet blown cellulose between the studs and dry cellulose above the ceiling.

To answer scercrcr's questions, the number we got from the Crane was an average of R-3.6 for the siding. This is a continuous number not broken up by stud bays like fiberglass. The corner pieces and trim is all insulation backed.

The warranty is for the life of the home and is transferable so I guess the manufacturer figures it will last a while.

putting the insulation board directly on the house instead of on vinyl will allow the full insulation R-value to be achieved.
by putting the insulation board on the vinyl, which is far far from air tight, you reduce the R-value significantly.
it is not a continous number/R-value.
save the added cost of insulated vinyl, add 1" closed cell foam board with all seams taped (this is what is ment by continous insulation, btw) then vinyl sididng(uninsulated)
on top of continuous foam insulation.
1" closed cell is about R=6.7 1/2" would be R-3.3. Either would be a better performance because it is installed in a manner that is truly continous.
it was around 1960 when we stopped building with strips of wood and switched to sheathings, that air tighness became so much easier to achieve. to inslate vinly siding is a step back to those times.

Thanks for your ideas but I was thinking about putting the 1" foam board underneath the insulated siding. We would then have to build out our windows a bit but it would be insulated well. I like the look of the craneboard because it looks like clapboard(or hardy) without the expense of the install. Has anyone put foam board behind their insulated vinyl?

waste of $$.
the foam sheathing in contact with the wall, properly nailed, seams taped and all penetrations sealed provides
thermal barrier on exterior of house.
however,
there are two methods of installing vinyl on top of foam sheathing. use foil/foam sheathing
on exterior..taped to seal..blah blah..1" furring strips are installed where vinly siding will be nailed. vinly installed.
use of foil faced sheating with furring strips will create radaint barrier on walls..reflecting heat out a benefit in hot climates.
furring strips will also allow for full nailing of vinyl.

second method would not entail furring strips, but vinyl would be nailed directly to foam sheathing. if nail guns are being used, the depth has to be set correctly and checked during use of nail gun, to assure that nail is not shooting through foam sheathing..sounds crazy. you would think, looking where you are working, that you would notice. but is is more about speed than quality.
you might have to be quality control!
best of luck.