Relay Continuous Current Ratings vs Size
Omron is a reliable company. If they say it's rated at 30 switching resistive, it will give you the stated 100,000 operations life switching 30A resistive under the stated test conditions.
Take care that the life ratings of relays (in general, and including this one) are with no diode across the coil so adding a diode (rather than something that allows the coil voltage to go much higher) may reduce the relay life.
As far as continuous current rating, the overcurrent failure curves from this datasheet indicate that it might be a bit close at 85°C Ta and 25A continuous.
So maybe you're onto something there. Looks like if the ambient is hot you might want to keep the current a lot lower than 25A to be conservative.