Thermal regulation in long inkjet printhead

An inkjet printing system comprising:

• (a) an inkjet printhead comprising:
• a rigid elongate manifold having at least first and second neighboring parallel ink supply channels extending along a length of the manifold between respective ink ports positioned at opposite first and second ends of the manifold;
• a plurality of printhead chips mounted to a lower surface of the manifold, the first and second ink supply channels supplying ink to the printhead chips via ink outlets defined in the lower surface;
• wherein:
• the first end of the manifold comprises a first ink inlet port for the first ink supply channel and a second ink outlet port for the second ink supply channel;
• the second end of the manifold comprises a first ink outlet port for the first ink supply channel and a second ink inlet port for the second ink supply channel;
• (b) a first ink delivery system configured for delivering a first ink to the first ink inlet and flowing said first ink along the first ink supply channel in a first direction;
• and
• (c) a second ink delivery system configured for delivering a second ink to the second ink inlet and flowing said second ink along the second ink supply channel in a second direction opposite the first direction.