Exporting LTspice waveforms to txt or csv
LTspice, by default, uses a variable step size which has large values when nothing critical happens (e.g. steady-state) and it tightens them for transients and such. For a specific time-step you can use the builtin maximum simulation step, for example:

.TRAN 0 {final_time} {start_saving_data_optional} {time_step}

Adding an options card such as: .OPT plotwinsize=0 will force the compression to be turned off, as well. There are more options to play around, see the help file or, if you have more intimate questions, ask in the Yahoo's LTspice group (I hope this doesn't count as advertising)