Folding Bikes-How far can you go on them?

Thinking of getting a fold up bike to cycle to a train station 4.7KM/2.92 miles. Is that further than folding bikes are built for? Would smaller wheels make it take forever?
Update: Why is it hard to keep balance? Ground wise, its all flat, no hills or anything and its a reasonable road surface. Just some fast cars :S
10 answers 10