To me it depends on these factors:
1) What sort of compost are they in as soil-based ones retain more water than peat-based.
2) Are your seedlings getting any warmth as this will affect the retention of moisture in the compost.
3) My best advice is to lift your pots or trays of seedlings. If it has some bit of weight to it then leave well alone. If it feels rather light, plunge them into a tray of water until you see the surface of the compost go a bit darker, take them out, drain out any excess water then put them back where they were.
Seedlings only have tiny roots and don't need more water than they can take up or you'll lose the lot.