My hall bath has a 97 inch vanity. It doesn't seem too long but it does have 2 sinks. If my vanity only had 1 sink I think it would look like someone forgot to put in the second sink. Yours at 90" might look that way too. If you kept it at 72 inches but want a little more drawer storage maybe you could use a 30" sink base with 21" wide drawers or a 30" base with 20" drawers.

Or you could stick a pantry/linen closet in the mix, usually against a wall. Most of my customers want as much cabinet space as they can get/afford.

Rick

In my master bath my vanity is 124". I do have two sink cabinets and two drawers but the middle section is a sit down vanity with a shallow drawer. I think it looks fine. If storage is a concern, maybe a built in linen closet is more useful than extra drawers? I could have made mine longer but opted for a linen closet which I love.

It's true that having two sinks adds both to plumbing fees and double's the cost of sinks and faucets...........but is resale a consideration? I would expect to see two sinks in a large master bathroom. Some potential buyers would refuse to buy, and others may over estimate the costs to add one and offer a lower bid especially if you live in an area where two sinks are the norm.

Unless you think you'll never ever sell your home and neither will your heirs (and that's simply not practical), pay the extra dollars and put in the double sink. In the grand scheme of the house, this is a small thing. I daresay that 95% or more of future homebuyers will want a second sink in the master. You have the space, so why cheap out on that? Just because you don't now get ready at the same time, that could well change in the future, for an evening out, or you may find that if you had it, you'd use it.

Sujafr echos my thoughts exactly. If your going to do it, may as well do it in away that will help your value in the long run.

Or you can offset the single sink, put all the plumbing for the second sink in, and let the anonymous future buyer put in a new countertop and sink if they want to add it. If someone passes on my house because it's missing a sink and that's the only reason...well, whatever.

Maybe a trough sink to help with the proportions?

I live alone and have 9 ft. of cabinets in the master bath, with a sink in each end cabinet. It looks balanced and works nicely if guests at times use that bathroom. They then have a pristine second sink. In the big scheme of things, we're not talking about that much more money to add the second sink and faucet. And no, a 106" long vanity in my bath does not look too long, so 90" should look fine in yours. I would put a 27" sink cabinet at each end, with a 36" 3 drawer bank in the middle, for a 90" total. If you and DH are sharing the drawers, a middle drawer divider would take care of that. A 36" wide cabinet makes much better use of space than two 18" cabinets. Also, I love the luxury of having all that counter space in the middle to lay out clothes, or sometimes even for wrapping gifts.