It isn’t a good idea to trickle charge lead acid batteries continuously. A standard trickle charger will provide a constant voltage and will indicate when the battery is charged because the current drawn reduces, but as the voltage stays high it can cause high temps and water evaporation and corrosion of the positive terminal. Think of it like filling a bucket from a tap, if you keep the tap on the bucket overflows and the water that overflows might cause damage.
Most “intelligent” chargers / conditioners will allow the cell voltage to reduce to the “float” level effectively creating a very shallow discharge / charge cycle which prevents this damage from occurring. They only come on the replace water that has evaporated from the bucket, so it never overflows.
The important thing here is to know your charger, if it is a basic trickle charger then don’t keep it on all the time, use it for a few hours every week. I have an intelligent charger but only use it every few weeks anyway.
There are risks either way, but discharging a battery below the minimum final voltage will also cause permanent damage, so you have to try and keep things somewhere in the middle.