Make more clear how often a user has to check their offers and trades

[HenrikJannsen]

Renamed the original title as we have the 1 day limit in the trade rules but we should improve visibility of that info and extend it to offer makers.

[HenrikJannsen]

Actually we have that line in the trade rules: - If the trade cannot be completed instantly due to longer Fiat transfer times, both traders must be online at least once a day to monitor the trade progress

I might not be very visible and I saw some user asking... Also it does not say anything about a maker who has an offer out, how often they need to check.