This is the first thing you'll need to consider before you go to make a record. The answer to the question isn't very simple actually. Not unlike the CD or cassette tapes, Vinyl Records only allow for limited duration of playback time per side. This isn't very straight forward because the level at which the record can be cut, and the maximum duration per side can be dictated by the recorded programming. The RIAA has set standards to be used as a guide, however part of the processes in making records is to provide the best listening experience possible. Master audio needs to be reviewed and the cutting engineer runs test cuts to understand how programming translates to lacquer discs. Once the engineer has validated their assumptions through various test cuts or the use of a reference disc, they're able to determine how much level and fidelity will be possible relative to overall duration of the side. That being said, the rule of thumb is the shorter the better. Low end frequencies create wide grooves, and cutting level (volume) is also associated with the width and depth of the groove. The wider the groove the less room you have on the surface of the disc to cut. Loud cuts that contain a fair amount of low end ultimately need to be shorter. If your sides are long, then the engineer might need to cut at a lower volume making the grooves smaller to ensure there's enough room on the disc to fit the entire requested programming.
Another thing worth noting is you want to sequence your record so that the sides are balanced. If you have a single side that's 6 minutes and the other is only 3 minutes. The shorter side will be cut to the same db level as the long side to ensure the volume of the record is congruent. Otherwise when the listening flips the record they'll need to turn up or turn down their stereo, interrupting the listening experiences.
All recorded content is unique, and so all records are unique. A common question we get at the test pressing phase is; why are my records not as loud as other records in my collection? The short answer is your sides could just be longer and/or your programming is unique and different than the record your comparing it to. The chart pictured in this post is a guide. It should give you a basic idea on what's possible. With every project we strive for the perfect cut; Max level (volume) without intruducing distortion or sibilance.