My DD is 6 months old and i have the same problem, she will usually nap 1 hour and sometimes if i am luck it will be 1.5 hours.
I do continue to resettle if it is only 1 hour because after only about 1 hour up she is very cranky and also she feeds every 4 hours so it does distrupt this.
I know what you mean though cause if DD wakes at 1 hour, she will usually talk for 20 minutes or so, then she will cry so i go in, but then she only has about 40 minutes left of her sleep anyway and I usually can't get her to resettle in this time.
I have perservered though and some naps have extended, i think i will try for a couple more weeks to extend and then maybe go with the flow.
Other times she can sleep for 1.5-2 hours so maybe she knows when she has had enough sleep?