The best way to join them involves a 1/2 inch router and a template. If you have that kit then you can join them and maybe reinforce the join with tenons it's fine to join anywhere. I would recommend choosing a worktop that comes in the longer length. If you really only need it to last five years, join it with a jigsaw.
Thanks! Ikea only do a 3.5m length annoyingly. I've improvised with a 35mm bit for cutting cupboard door hinges to create the whole to seat the zip bolt thingies in. It doesn't look great but it's only (long-term) temporary i guess.
Way back when I used to join worktops like that I would use a colour matched sealant in the joint, even if it was a tiny joint, just to stop water getting in and swelling the particle board.
The best way to join them involves a 1/2 inch router and a template. If you have that kit then you can join them and maybe reinforce the join with tenons it's fine to join anywhere. I would recommend choosing a worktop that comes in the longer length. If you really only need it to last five years, join it with a jigsaw.