Gas Water Heater Delayed Hot Water

I know someone who has a gas hot water heater.

Suddenly, it seems that the time it takes for hot water to reach the sink has increased drastically, yet when it reaches the sink, it's as hot as normal.

Any idea what I should look for as the cause?
Thanks for any advice

One thought is, did they change the type of water heater? Changing from a tank-style to a tankless pretty much guarantees an increase in wait time.

Any changes in home? For example a young person living there uses sink in morning and this sink is half way from water heater to the sink in question. When the young person uses this sink, hot water is now half way to other sink.

Then young person moves away. Now hot water must come all the way from the water heater.

So any changes in work schedules, people living in the house, etc.?

Then city water pressure can change. Could be lower and water now runs slower. Notice that?

Then there is "crud" in water lines. this crud can clog valves, small openings in water heater inlets/outlets, the valves under the sink, the faucet valves, and the aerators on the faucets. This could cause the water to flow more slowly.

Does the cold water run faster than the hot?

kansas Master Plumber

yet when it reaches the sink, it's as hot as normal.
does the water stay hot as long as normal?
There may be a restriction in the hot water side
just thinking outlaud

Thanks for the replies, they are food for thought.
In this case, the water heater is the same one with no changes in who lives there or how they use water.
This water system is on a well.
Since I don't live there, I'll ask more questions to try to get more info that may be helpful when I'm there next time.