You can. Here is an example.
redis 127.0.0.1:6379> hset key f1 1
(integer) 1
redis 127.0.0.1:6379> hset key f2 2
(integer) 1
redis 127.0.0.1:6379> hvals key
1) "1"
2) "1"
3) "2"
redis 127.0.0.1:6379> expire key 10
(integer) 1
redis 127.0.0.1:6379> hvals key
1) "1"
2) "1"
3) "2"
redis 127.0.0.1:6379> hvals key
1) "1"
2) "1"
3) "2"
redis 127.0.0.1:6379> hvals key
Use EXPIRE or EXPIREAT command.
If you want to expire specific keys in the hash older then 1 month. This is not possible. Redis expire command is for all keys in the hash. If you set daily hash key, you can set a keys time to live.
hset key-20140325 f1 1
expire key-20140325 100
hset key-20140325 f1 2