In the UK METARs are generally issued every 30 minutes (obs are made at hr+20 and hr+50 so that they can be issued on the hour and half hour). If there is little change, or the finances aren't available(!), then this may decrease to hourly.
TAFs come in three forecast periods: 9hrs, 18hrs and 24hrs - but there is only one station in the UK (that I know of) that issues 24hr TAFs: RAF Brize Norton. The most common is the 9hr TAF. only selected larger stations will produce 18hr TAFs.
Civvie stations tend to issue for periods 1000hrs-1900hrs, 1300-2200 etc. Military stations issue 0900-1800, 1200-2100 etc.