There are a few trains of thought but one is - maintain close to whatever speed you were cruising at for the climb - climb rate will be slower but thrust won’t go to maximum for the climb, especially for a gentle 500’/min. As a bonus, it’s also quieter and won’t disturb the passengers who may be trying to sleep.
You don’t really want to have to accelerate once level as at altitude it can take a long time and a lot more thrust.