The best solution is to move your prospect to the Dedicated Server.
Lots of building pieces is a cause for performance degradation.
As are mined nodes, cut or burnt trees, mined rocks etc.
Basically every change you make on the map causes so-called Delta Data.
This Delta Data accumulates over time, causing performance degradation.
To combat this, run Thumper to regenerate mined nodes in it's area of influence (beware the local wildlife), run Localized Terraforming Device to regenerate trees in its area of influence, enable foliage respawn and big rock respawn (in the game settings).
Keep your buildings sensible sized (more building pieces need more structural stability calculations), keep your power and water networks sensible sized (every producer, consumer and storage device needs extra compute power to calculate the production, consumption and the effects in storage of power and water).
Don't accumulate too many tames in one location (their food and water levels as well as their pathing all cost compute power).
Running the prospect on a Dedicated Server splits the computer load between the server and the client.
That's why you generally have better performance when running the prospect on a DS.