I used Shutterfly for a wall calendar (Ireland) a few years ago. I was pretty pleased with the results, but got tired of their endless spam and discount offers EVERY SINGLE DAY. If you've used Shutterfly for any length of time, you've probably figured out that you'd be crazy to pay full price for any of their offerings because there are always promo codes and sometime fairly large discounts.
I am a serious fine art photographer (seven exhibits in three countries to my credit) in addition to my day job as a scientist/university faculty. If you are serious about high quality prints, you might want to look into
https://bayphoto.com. Their prices are not bad and the quality is quite impressive. They also have knowledgeable techs you can talk to on the phone--I would recommend you call them and discuss your project. Many serious amateurs/pros I know use their services for things that can't readily be printed on an inkjet printer--metal, acrylic prints, calendars, mugs and the like. They have a ROES/remote ordering system (i.e,. an app) you can install on your desktop. It allows you to configure whatever it is you want to print and send it with one click. Their shipping is pretty fast.
They fcuked up and printed the first calendar I sent them (France) without a cover. They were pretty slow to answer my e-mail about this, but they did refund my money. The calendar app is a little weird; I did the months out of order and had to specify that I wanted the months printed in the correct chronological order. Otherwise, I would have received a calender with December before October. Nevertheless, the calendar looks great and the paper is terrific!
If you wanna be a rock star, I recommend you look into RawTherapee for postprocesing. It will do bitmap images (jpg tiff) in addition to RAW. In some respects, it absolutely nukes Lightroom (but it is NOT an easy program!). And it's free.
http://rawtherapee.com(Pro tips: If you're going to post-process your own images--which you should do if you are serious--be sure to turn OFF "color correction" option in the BayROES app.
Also, unless you are a pro with monitor calibration, ICC profiles, and soft-proofing, I would recommend you print a proof or two to see how well their prints line up with what you see on your monitor! Don't waste 500$ on all of it only to find out that all of the prints are too dark or light, or the colors are way out of whack with what your monitor displays!)