I have tried mixing the two, and for me it didnt work.
When I was younger (late teens – early twenties) I was purely a cyclist and got the odd top 10 sports cat placing. I was quite happy with this at the time, however then I joined the RAF and got into running, I had more of a natural talent for this (despite being 5ft7), and got to a half decent level, top 5 county level at x-country. When I started getting running injuries all the time, I thought that to take the load of running, I’d get back into cycling and try my hand at duathlon, I found it hard to fit in the time to train to a decent level at both events,
If you have the time, and the dedication, spiting the training is great for all round fitness, and injury prevention. Plus training for the 2 events can help relive the boredom that can set in. Go for it!