I’ve inflated the tires to 3bar (43.5psi) on Tuesday, rode Tuesday and Thursday for about an hour.
Now (Friday) the front tire (showing no sealant stains) has 2.75bar (39.9psi) and the read tire is down to 2.5bar (36.6psi), corresponding to a loss of 3.6psi (front) vs. 6.9psi (rear).
From what I’ve read elsewhere this is still within limits.
Using patches (instead of plugs) when at home makes sense.
Today I had another look at the tire: I still can’t see any punctures from the outside (contrary to my road bike tires with latex tubes where I easily can spot many).
At least one spot seems not to be fully sealed because the sealant stains are not completely dry, indicating that sealant continues to leak.