I wrote to Sony Ericsson and they gave me the official lowdown on charging the T610.
First charge has to be for 16 hrs with PHONE TURNED OFF
After this you need only charge the phone for 3-4 hrs.
Should the phone become completely juiced out you will need to do the first charge all over again as if it is a fresh battery (16hrs with the phone turned off!)
This source is from the official Sony Ericsson T610 from the UK.
Hope this is useful to all those wondering about the battery.