Didn't need sealing, it has weathered well over winter, but it will need a clean because there are some bits of green where algae or something has formed but we have a karcher pressure washer anyway with the patio attachment so will be giving it the once over with that.
Re limestone the staining part was the reason we avoided it. We are very lazy and just wanted to wash it a twice a year! Didn't want to mess around with sealant etc.
My builder was fab and he had sandstone put down years ago, never sealed it and just washes it around 4 times a year which is hardly taxing. (he's a perfectionist which is why I chose him) He had also laid around 20 sandstone patios in the last 6 months! So it was easy for him and his builder mate to lay ours without even thinking about it.
Mine looks different wet than dry - you can see that in my photo as there is a wet circle and an arc from where I had used the hose pipe for something.
I actually got mine from this company, I had to order two packs from here My photo only shows one part of the patio, it goes round the extension which is the wall on the right of the photo.
Always go an see stuff in real life, we went to a quarry but didn't order from them as the range was 18-25mm which can be quite a difference in slab thickness.
Even though mine was 22mm calibrated so technically all the same, the bottoms were pretty much flat but the tops have different thicknesses as the sandstone cleaves so it isn't all flat like a concrete slab, there are natural undulations if that makes sense.