I think part of the prob is that you make so much more mess when you spend so much time at home, and it's too cold to get out as much as you might otherwise.
I think Lara's hit on it really. When it was just dh and I at work/uni, our house was significantly cleaner! But kids home during the day, are relentless. If you give my #2 a spare 5 minutes, he'll find a washing basket and take great delight in pulling things out and throwing them - and I sort of figure...well, that's a safe 10mins of entertainment for him, maybe that's 10min I can spend having a cuppa.

So I guess that's what we have to look forward to - warmer weather in the short term, and school in the longer term.