BTW, here's a description how you can check your hosted server's TTL (copy from Rackspace site)
Checking When a Cached Record Will Expire
DNS uses caching, this reduces the load on authoritative name servers but means that sometimes records can be out of date. If the authoritative and non-authoritative answers differ, this means you will have a cached response from the resolver name server you are using. The length of time a record is cached depends on its time-to-live (TTL) value. This is a number specified in seconds. To see how long a record will be cached for requires the debug switch.
C:\Users\Administrator>nslookup -type=A -debug rackspace.co.uk
opcode = QUERY, id = 1, rcode = NOERROR
header flags: response, want recursion, recursion avail.
questions = 1, answers = 1, authority records = 2, additional = 2
22.214.171.124.in-addr.arpa , type = PTR, class = IN
name = cachens1.lon.rackspace.com
ttl = 2466 (41 mins 6 secs)
bla bla bla bla....
The first "Got answer" section of this example is used to get the hostname of the server you are requesting the A record from, in this case cachens1.lon.rackspace.com.
So from this you can see that the name server being used by the client computer will keep reusing the same A record for rackspace.co.uk for the next 4 minutes and 39 seconds. If you were to run the same command on the authoritative name server you would see what the current maximum TTL for the record is.
See the ful article at http://www.rackspace.com/knowledge_center/article/nslookup-checking-dns-records-on-windows#3_CheckingCache