If you buy a share because you think overall market is moving up, then you should hold until you think ASPI is at peak.
If you buy a share because you think earnings will be good (e.g. TKYO), then hold on at least until the quarterly results are published and hold on till next quarter is you expect good results to continue (if you think ASPI will keep increasing)
If you buy a share because there's foreign interest, then monitor the inflow/outflow situation
If you buy it because of technical support, monitor any resistant levels etc
Be careful to monitor - be proactive!
I personally feel that this is a good time to buy - market is showing good signs which go beyond the ASPI numbers. I would stay away from silly share and concentrate on shares which showed increases in profits during last quarter and trading below Sector PE. This is the last chance to buy before quarterly reports are published and I expect the ASPI to move up once they are.