Should I change the tilt angle manually throughout the year?

If an array tilt angle can be changed, that is up to each solar PV system owner.  Most grid tied systems are not changed, as they are mainly roof mounted and may result in only a 5% increase in production.  Off-grid systems may need the extra production during  winter months in order to charge the batteries, which then would make sense to change the tilt angle.   Ground mount arrays can be made to easily change the tilt angle during the spring and fall equinox.