Walk down to the pit on a dry afternoon and look at the pump before the wet season starts. You are not testing the pump yet. You are establishing what normal looks like for this house, so the change is visible when it comes.
What the pump is telling you
A sump pump sits in a pit and lifts water out when the float rises. Most of what it does is quiet. The early signs of trouble show up as a change in rhythm: it starts more often, it runs longer per cycle, or it runs without rain to explain it. None of these means the pump has failed. Each one is a reading you can compare against the reading you took last time.
What to log
Keep a simple note by the pit or on your phone. Record the date of each wet spell, how many times the pump starts during a heavy rain, roughly how long each run lasts by the clock on the wall, and whether the water rises to the same level before the pump starts. Note any noise: a grinding hum, a rattle from the discharge pipe, or a clunk when the pump shuts off. Write down the pit depth at the start of the season if you know it.
Common causes to check
Several causes come up often enough to check first. A float that snags on the pit wall or on its cable will make the pump run late or not at all. A check valve that lets water drain back into the pit will make the pump cycle more often, because the same water gets lifted again. A discharge line with a partial clog or a sag will make the pump work against more resistance, which shows up as longer runs. Look at the float path, the check valve, and the discharge line before you decide the motor is the problem.
Where age fits
Age is a planning input, not a verdict. Find the install year from the house file or from the label on the pump housing. If the pump is well along its expected service life and you are logging a steady change, the reading supports planning a replacement window. If the pump is young and the change is sudden, check the float, the valve, and the line first, because a young pump with a stuck float looks the same from the pit as an old pump in decline.
What to ask before you call anyone
Ask the technician to test the float travel, check whether the valve holds, and measure the discharge flow if they have the tools. Ask what the log shows against the install year, and what replacement would involve, including whether a battery backup is part of the same job. Ask them to write down their findings so you can compare next season's readings to them.
The next step
Keep the log through the wet season and read it when the rain stops. A steady change over several wet spells is the planning signal. A single odd night is usually the float or the weather. Either way, the written record lets you decide with evidence rather than memory.