By "needles": I mean two needles joined by a piece of dental floss type plastic wire, the total length of which (including the needle "ends") is 40 cm. The c. 7mm needles (they were old ones I found of my Mum's) were, in total 38cm (I've just measured them) from the tip of one needle to the tip of the other, including the length of plastic wire joining them. They are always described as "needles" in the patterns I have used so far (the two Icelandic ones - free downloads :)) even though they are technically a single item.
I really didn't have any problems down to 15 stitches - and as I say, given that it was the last row, I could have finished the penultimate round with 30 stitches and then knitted the last round onto a single 7mm needle, ie pushing all the stitches to the one end of the circular needles and knttining from that onto the "standard" needle.
Trust me - I am not an experienced knitter: I started again just before Christmas not having been near knitting needles in nearly 20 years. Back then, I had to refer to my mum for advice for just about everything - she was a very experienced knitter. This time I am no longer able to ask her for much advice (she has a rare form of dementia :( - although she has been able to confirm that she also tended to knit tight and her cast-ons were too tight, which, given that she initially taught me was kind of reassuring), so I have to keep on referring to the internet for how to do anything more advanced than "knit one, purl one"
I even had to look up what "moss stitch" was! 
My Icelandic vest looks good (even if it is a bit tight) - and before starting my latest effort (a Patons interndiate pattern for a reversible shrug with one half lacy and the other a rib pattern), I did take the time to knit a tension square
- espcially as I couldn't find the yarn that they suggested.