We had first generation Tamron 18-270. We traded those in for the 2nd generation. It is a better walkaround lens.
On a June trip to the southwest we had windblown sand get into them. So we sent them to Tamron for cleaning estimates. For lenses we paid just over $600 for....they want $400 each to clean, recalibrate...etc.
For an extra $250 per lens...we could purchase have totally new units.
Not favorably impressed at all with how easily windblown sand got in when the lens were never changed during shoots. Not either impressed with Tamron's repair cost estimates.
I think we have spent our last dollar on a Tamron product.