Kooky, yay for being home! So glad it is all going well with Joe.
Ses - have to say that I would be going with encouraging DS to self-settle now. DD is 6 months next week and we are just going through that process now, as I kept thinking she would just get it. At 5 months I started the "No Cry Sleep Solution", which is a softly softly approach to get them to learn to sleep on their own - it has helped, as I started DD getting used to not falling asleep at the breast every time and she learnt to fall asleep in my arms too. Now, we're following the Baby Whisperer to get her to fall asleep on her own in her cot, as she was just waking far too many times in the night and me feeding her and then not being hungry for her feed first thing. After first night she did 7 hours between feeds and 6 hours asleep (unheard of before and if only I had managed to sleep for allof that, but was awake 1 hour before her) - has not been repeated to such a good extent, but I'm giving it two weeks to see how it goes. Do need to get stricter in middle of night, as she's not taking full feeds when she does wake, ah well....
Anyway, my moral of the story is that once they get to 4 months, I would start a certain amount of helping them to self-settle, as IME it does not happen of it's own accord if they have learnt to feed to sleep. Sounds like your DS is learning some of it himself and so it must be working for you. Do go with what makes you happy, but if you have a goal of him being able to do it, i would start little steps now.
Kayz - good luck for theory test.
to everyone else - ridiculously early start here with DD at 5.30am - grrr (dreaming of the time when that is a start at 5.30am preceded by a decent length of sleep beforehand )