I co-slept with DS1 from 0-6m. Then he went into his cot, but I would still sometimes have him back in with me - until he was 18mo and we shipped all our stuff to Australia, and he came back in with me.
DH and I have VERY different sleep patterns (about 3h shifted apart - he likes to go to bed at 9 and wake at 5 or 6, I like to go to bed at 12 and get up at 8) and DH also apparently "needed his sleep" because "he worked" (as if I didn't need mine, or I didn't work, but hey) so it worked for us that DH stayed in the spare bed and DS1 was in with me.
When we got to Australia, the situation was such that I couldn't get Ds1 to sleep in the cot any longer, so he stayed in with me. When we moved into our house, there were 2 bedrooms, but DS1 wasn't having a bar of sleeping on his own (still only 21mo) as he was so disrupted - so I slept in with him, but we bought a super kingsize bed for the master bedroom, on the principle that if we all needed to sleep together, we could.
However, we still had the differing sleep patterns - and DS1 followed mine, not DH's.
Then I got pg with DS2 - got SPD and acid reflux and had to kick DS1 out, he he went in with DH for a while (no problem in the superkingsize bed!
) and then we built him a new bedroom. As he was 5 when he moved into it, he was quite happy to sleep in there; plus it gave him some space of his own once DS2 had arrived.
DS2 - still in with me at 2.6yo. Not quite sure what's next but DH and I still have disparate sleep patterns, and he likes a soft pillow-top mattress, which I can't sleep on because I have a bad back; ideally we need another bedroom for DS2! And then I can keep the one I have now, DH can keep the master bedroom and both boys will have their own. Spoilt, yes - but with 5y difference, and DS1's bedroom is quite small, I don't want them in together. If all else fails, we'll get 2 single mattresses for the super kingsize bed, one for DH and one for me (to get around the softness problems) - and DS2 will have the bedroom we're in together now - but that still won't alleviate the time difference problem. :(
I don't have any problem co-sleeping, except when DS2 clings on to me like a limpet; but that's fairly rare, he likes his own space as well.
So this is a long rambling post but hope it explains why we do it. I've never had any problems with DS1 getting up in the middle of the night regularly - he does it very occasionally if he has a bad dream, but he goes into DH, not me, so it doesn't bother me 