This is my experience with sensor cleaning;
Not long after I first got my camera, nearly 18 months ago, I noticed there were a couple of spots on the sensor & what appeared to be a faint fingerprint! I just presumed it was there from manufacturing process & hadn't been cleaned/inspected thoroughly.
I had a rocket blower, but that didn't clean the spots away (they only showed against bright sky, so cloned em out)
After a few weeks I bought another lens & one of those wet cleaning kits (what a faff to use & a bit daunting for a newbie! )
After the initial cleaning all seeming well for a few months, then I became a little frustrated when I noticed a couple of dust spots again, which I couldn't shift with the rocket blower! So I got out the kit i'd bought & again reluctantly cleaned the sensor (using another 1/3rd of those expensive swabs )
This time I couldn't seem to get it `squeeky clean`. It was as though there was a film of grease on the sensor, almost looked like oil on water does in the sunshine.
From that day my pics just lacked that pin-sharp quality that I knew my lenses were capable of. By this time though, Autumn had arrived & good light was in short supply, so didn't think too much of it. (tbh I was HOPING the light WAS the problem I think )
On now to a couple of months ago, so I decide to clean again (sigh) using up most of the remaining swabs, only to find the same result! NO WAY could I get it smear free & myself completely happy with my bird pics. The feather detail was just not quite as sharp. So beggar it, I finally accepted defeat & took it into a local camera store 2 weeks ago. They cleaned the sensor & focusing screen (possibly the mirror too). Dropped off, then collected within 90 mins.....SORTED!

The best £35 i've spent. I wish i'd done it last year instead of buying that expensive kit & suffering 6 months of frustration.
I also learned that some of the `cleaning fluids` don't have an infinite shelf life, so maybe mine was part of the problem too?
So in future, apart from changing lenses as carefully as poss, i'll occasionally be using the rocket blower, speck-grabber/actic butterfly DRY methods etc.
IF/when dust specks get bad enough that they annoys me & I can't easily remove them, i'll be taking it back to the store for them to do it.
Sorry for the long winded post, but thought it might help others who are fairly new to Dslr's so you can decide whether `do it youself` or pay up. I know which I now prefer
