There are several threads discussing that the RX-V2500 runs hot and that the "continuous fan mode" from the DIAG menu has no effect. Since this is now a relatively old receiver, I opened it and manually tweaked the fan curves. Thought it might be of interest to people still happily using these receivers like I do. Link.
System 1: Yamaha RX-V2500 + 4x Bose 501 Series IV
System 2: Marantz NR1402 + 3x Boston Acoustics CS26 Gen. 1
System 3: 3x JBL LSR305 + JBL LSR310s