It can vary by the type of bike, and it can also vary by the brand of the bike.
Some of the maintenance items on the schedule for my bike are set up as time or mileage, whichever comes first.... plus the mention of riding in wet or dirty conditions. Example, brake and clutch fluids are every 16,000 miles or 2 years, whichever comes first.
BMW motorcycles seem the more demanding as far as what needs to be done, and when to do it. Also, probably the one that could requires the assistance of a dealership the most, considering the big manufacturers.
If there are models of motorcycles that you are interested in, search to find a copy of the maintenance schedule online and then read through it.
There can also be gaps in a manufacturer's maintenance schedule that seem baffling. On mine, there is no maintenance requirement for the fork oil or differential oil. That means I need to make a decision as to when I feel that this should be addressed. The experience and recommendation of a good, honest dealership service department can come in handy here. They can recommend when to change the fork oil based on what they've seen in real world conditions when they've torn down forks down to rebuild them.
Some items that should seem simple, can be difficult on a motorcycle, require special tools, or require the removal of other parts (removing the gas tank to get at one bolt for the alternator). Motorcycles can be a much tighter package. Changing the air filter on my GL1800, is a 3 hour, 2 beer job. Sure, some can do it faster....but I prefer to take it easy and do it once. However, replacing the brake pads is a 15 minute job.
I look at the maintenance schedule, and perform all of my maintenance for the coming 12 months, every February. Anything due for attention in the coming 12 months or 10,000 miles gets done in February. This includes wear items such as brake pads. I don't want to have to tear into the bike in July to replace brake pads, when it could have been done in February. Granted, I am wasting some money by taking a $30 pair of brake pads out of service early, but it is convenience versus cost.
Finally, once you buy, spending the money for a factory shop manual is usually a good idea as well. Usually less than $100.