Yeah, for a huge bit like that 900 doesn’t seem crazy. Of course a lot of other factors play in, like cut depth. Going that speed at the bit’s full cut depth of 0.25 inch would be hard on the blade and hard on the material It would also create a lot of pressure on the wood, so you’d need to consider how the material is being held down and if it can handle that much push. But if you were taking off a millimeter at a time, 0.03 inches, and the material was very securly held down, yeah, the blade and material would be fine at that speed.
You can play around with the chip load too. If you’re just trying to remove material, you can go with the highest suggested chip load. If you wanted a smoother finish, you can try a smaller chip load.
We can reverse engineer what you did before too. Chip load = feed rate / (spindle speed X number of flutes). So, 100 feed rate / (15,000 x 3) = Chip load of 0.002 which is smaller even than the recommended size for a 1/8 inch bit.
I use a 2 flute 1.125 diameter bit on hardwood and run it at 684 with great results. Don’t be afraid to speed things up a bit 
This article has a great explanation of all of this too: https://inventables.zendesk.com/hc/en-us/articles/360012848433-Calculating-Your-Cut-Settings-Basic-Feeds-and-Speeds-Information