BI 4.1 SP1 to other Service Pack upgrades

Hi,

Currenlty we are on SAP BI4.1 SP1 since Dec2013. I see that SAP has released SP2 and SP3. My question is when to make the decision of upgrading to higher service packs? Is it necessary to upgrade if the system is running fine with out any issues? Will I be able to upgrade directly from SP1 to a newer version of BI in future (lets say BI 5.0)?

we are using a custom build java UI as the front end and the servers are Windows 2008 R2.

Thanks!