John,
I can't recall how long it took for my free-standing Warren to begin bearing - probably 10 years - but it is grafted on P.communis seedling - so the 'standard' rootstock possibly caused it to be even longer than if I'd put it in an established tree or on quince or a dwarfing pear stock.
Because Warren (and it's near-mirror-image, Magness) are pollen-sterile - and not especially attractive to pollenators, many pear enthusiasts are now recommending grafting branches of Warren & Magness into other more-attractive(to pollenators) varieties to improve likelihood of fruit set than if you have a full free-standing tree of either.

Mine bears moderate crops, but is in close proximity to a dozen or more other pear varieties.
Not my favorite pear - I'm not especially fond of the soft, 'butter' types - but the deer like it.

Magness or Warren on quince rootstock seems to bare early enough.

I've had one warren at a farmers market, and it was very very ordinary. Maybe not ripened properly; but I'd expected better after hearing for years it was gods gift to pears.