Time for an FYI Design Hack and this is one of my fave Photoshop Hacks! This is what we use in industry to elongate areas of imagery. It's quick, clean and concise. You can use the Clone Stamp Tool for this kinda thing, but this is soooo much better. Please note: this doesn't work well with busy patterns or textures, mainly block colours and block patterns!
If not, just post your question in the FYI Forum and we will answer it within 24 hours. Better yet — you may even get other members responding with their prime knowledge!