should I use a single fiber between two server rooms or split it into segments for easier maintenance/replacement?
Fiber doesn't require any maintenance. If you provide decent protection (duct, tube) it'll last forever. Always terminate fiber in a panel and use patch cables to connect equipment - an exposed cable is a vulnerable cable.
Only if more flexibility is required it is reasonable to use more connection points than directly necessary. Each connection is a potential breaking point, so less is better.
Also, local regulations may require using different fiber types outside and inside buildings. So, you'd terminate on the edge (in a panel) and patch in between.
But splitting the fiber into multiple segments connected via adapters can significantly decrease the quality/speed, no?
Yes, each connection loses some power and causes some attenuation, depending on connector quality, type and cleanness. Additionally, the pigtail splices cause some attenuation as well.
However, a short fiber run's power budget easily copes with those losses - keep in mind that the reach is in the hundreds (for multi-mode) or thousands of meters (for single-mode). 90 m is nothing, even with several connectors in the path.
You've specified SMF and Gigabit, so you're most likely looking at 1000BASE-LX10. Its power budget per 802.3 is 8.0 dB. Subtracting .04 dB for 100 m OS2 fiber, six connections of .2 dB each (three patch cables), you've got a total loss of 1.24 dB - plenty of headroom.