Starting 4 January 2010, the Sengkang LRT West Loop will run in both directions during peak hours, from Mondays to Fridays (except public holidays):
6.45am to 9.00am
6.15pm to 8.30pm
Source: http://www.sbstransit.com.sg/download/SK_West_Loop_Peak_Hours.pdf
How about Punggol East loop?