One powerful feature of PWL sources in LTspice is the ability to automate waveform behavior using additional parameters.
LTspice allows edits of time/value pairs in the Advanced dialog. To explore other syntax elements of PWL, right-click on the PWL statement in the schematic to edit further. To create a repeating PWL waveform, add REPEAT and ENDREPEAT to the PWL statement.
Repeat a waveform
Repeat a waveform a fixed number of times:
PWL REPEAT FOR 5 (0 0 1m 1 2m 1 3m 0) ENDREPEAT
Repeat indefinitely:
PWL REPEAT FOREVER (0 0 1m 1 2m 1 3m 0) ENDREPEAT
Figure 4 shows the original PWL example, along with a version of that waveform that repeats five times, as well as a waveform that repeats indefinitely (create multiple plot panes by right-clicking on the waveform viewer and select Add Plot Pane Above/Below).
Related Articles:
What is LTspice?
An Introduction to LTSpice
What is a Piecewise Linear (PWL) function in LTspice and when it should be used?
LTspice Tips - Mathematical Integration
LTspice Tips - Plot Manually Entered Functions