Scenario 1 (No one is playing)
a) They say that if you play games on cellphones like yours for more than one hour it suddenly heats up and it stops working. Is it true? Does yours have that problem?
b) I don't know, I haven't played long (yet)... / I don't know, I've never played long on my phone... / etc.
I don't know; I've never played that long on my phone. (Meaning: There are no occasions on which I have played for such a long time on my phone.)
Is that what I'm supposed to say? Any other options? How about using "for a long time" with "never"? Ex: I've never played for a long time on my phone, so I don't know if it heats up.
more than one hour was specifically mentioned, so I'd stick with that long in place of for a long time. Still, you can say I've never played for such a long time on my phone, so ...
Scenario 2 (One of them is playing)
a) They say
that if you play games on this cellphone for more than one hour it
suddenly heats up and it stops working. Is it true? How long have you
been playing?
b) *While playing, or after pausing the game* - I don't know, but I haven't been playing long... maybe half an hour.
I don't know, but I haven't been playing long... maybe half an hour (your suggestion) is OK.
Also: I don't know; I haven't been playing [that / very] long... maybe half an hour.
Is that what I'm supposed to say? Other options? According to my previous post, "I haven't played long... maybe half an hour" should be ok too, but for some reason I believe most native speakers just choose the continuous tense for this meaning. You believe right. I haven't played long suggests to me: I don't have a lot of playing experience -- there are not many occasions on which I have played. Adding maybe half an hour seems to add something contradictory.
CJ