On SH a reserve block is 6 days long with two fixed days off before and one after. Expect to be contactable up to 8pm the day before and either be assigned a trip, home standby or airport standby. Some periods can be very quiet some you can work every day. In practice, things are generally assigned earlier than 8pm and rarely changed. It is also possible to have a preference for certain length of trips or more standby etc. Not always granted but seems to work ok when it's quiet.
LH reserve periods are 10 days long with four fixed days of either at the beginning or the end. Only difference is that there is no airport standby on LH.