memcached as session handler 3x more reads then writes

Hi, Does anyone have an experience with using memcached session handler or possibly enough knowledge of internal php session processing who could explain why we do get 3x more session set commands then get commands? in data it is actually 1:1, same amount of data is being written as read which is what we expect but we are confused by set:get ratio. Apart from that session handling seems to be stable and with no problems. Thanks Stan here is memcache stat: [pid] => 12709 [uptime] => 98239 [time] => 1244029678 [version] => 1.2.6 [pointer_size] => 64 [rusage_user] => 359.122443 [rusage_system] => 533.937369 [curr_items] => 149742 [total_items] => 12530243 [bytes] => 412168840 [curr_connections] => 58 [total_connections] => 4983 [connection_structures] => 286 [cmd_get] => 5765795 [cmd_set] => 16948817 [get_hits] => 5683669 [get_misses] => 82126 [evictions] => 0 [bytes_read] => 50024940586 [bytes_written] => 50218604759 [limit_maxbytes] => 1073741824 [threads] => 4