I ride tubies, veloflex: so latex innerds, daily in very hot dry conditions. I inject orange seal when I glue them up, then after about 6-8 weeks as the sealant does dry up. This does depend upon latex versus butyl. In my experience, butyl tubes allow the sealant to remain liquid longer. Im not overly analytic about amount or when to refill, frankly i should be as I have been caught out with a puncture and dried up sealant. Id like to hear others experience as to how long before a top up.

inject 1-2oz once. depending on the humidity of where you live, check for remaining sealant (listen for sloshing a bit i guess, i've only used clinchers/tubes), and refill as necessary (shouldn't be more often than once every few months at a maximum).