The duration for still images can be defined in the prefs' import and file handling section. For text the behavior is "as designed". I don't see it as a problem, though, that's what the various layer shortcuts as listed on this page are for. No need to use the mouse to trim layers at all once you get the hang of it...
As Mylenium indicates, you can set some preferences that determine the default durations of layers based on still images and whether the new layers are created to begin at the current time or the composition start time. See "Create layers from footage items".
Thanks very much guys that has helped loads
Also learm these keyboard shortcuts:
alt [ -trim inpoint at cti
alt ] - trim outpoint @ cti
[ move inpoint to cti
] move outpoint to cti
i - move cti to inpoint
o - move cti to outpoint
note: you can trim multiple selected layers. And with trimming you can also extend length of stuff - don't just have to shrink the lengths.