If using 64-bit OS, then install Spotlight 64-bit edition. The 64-bit version’s memory usage should only be limited by the memory as available on the client machine. The memory usage should stabilize after about 24 hours. Adjust the following settings in Spotlight as well:
1. Refresh rates –Select View | Options menu option. Under Data Collection section, select 'Data refresh rates' option. Increase the number rates.
2. Chart History limits – Select View | Options | Appearance | Chart Configuration and change “Amount of history to display in charts” to 1 hour or longer
3. History Limits – Select View | Options | Storage and lower "History Limits" value